Please check Gemini's error log. In what stage did you get the error?

44 26/03/2010 15:31:06 Error Gemini could not insert: [CounterSoft.Gemini.Commons.Entity.IssueBareEN][SQL: INSERT INTO gemini_issues (projectid, issuetypeid, issuepriorityid, issueseverityid, issuestatusid, issueresolutionid, reportedby, fixedinversionid, summary, longdesc, revised, startdate, duedate, resolveddate, closeddate, issuerisklevelid, userdata1, userdata2, userdata3, percentcomplete, estimatedays, estimatehours, estimateminutes, visibility, visibilitymembertype, parentissueid, originatortype, originatorreply, originatordata, originatorprocessed) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?); select SCOPE_IDENTITY()] at NHibernate.Id.Insert.AbstractReturningDelegate.PerformInsert(SqlCommandInfo insertSQL, ISessionImplementor session, IBinder binder) at NHibernate.Persister.Entity.AbstractEntityPersister.Insert(Object[] fields, Boolean[] notNull, SqlCommandInfo sql, Object obj, ISessionImplementor session) at NHibernate.Persister.Entity.AbstractEntityPersister.Insert(Object[] fields, Object obj, ISessionImplementor session) at NHibernate.Action.EntityIdentityInsertAction.Execute() at NHibernate.Engine.ActionQueue.Execute(IExecutable executable) at NHibernate.Event.Default.AbstractSaveEventListener.PerformSaveOrReplicate(Object entity, EntityKey key, IEntityPersister persister, Boolean useIdentityColumn, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.AbstractSaveEventListener.PerformSave(Object entity, Object id, IEntityPersister persister, Boolean useIdentityColumn, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.AbstractSaveEventListener.SaveWithGeneratedId(Object entity, String entityName, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.EntityIsTransient(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.PerformSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.OnSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.FireSave(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.Save(Object obj) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558, Boolean x8b15d0e18e6888d9, ISession x45b53be31e53d68b) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558, Boolean x8b15d0e18e6888d9) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558) at CounterSoft.Gemini.DataProvider.xc0186e148e957052.x0dd7228622330700(IssueEN x22c77d60925997e9) at CounterSoft.Gemini.Business.x95da312ae9372c2e.x0dd7228622330700(IssueEN x22c77d60925997e9) at CounterSoft.Gemini.Presenter.IssuePresenter.CreateIssue(IssueEN issue) at CounterSoft.Gemini.Web.Api.IssuesRestHandler.IssueCreate(RequestDetails rd)
43 26/03/2010 15:31:06 Error Gemini could not insert: [CounterSoft.Gemini.Commons.Entity.IssueBareEN][SQL: INSERT INTO gemini_issues (projectid, issuetypeid, issuepriorityid, issueseverityid, issuestatusid, issueresolutionid, reportedby, fixedinversionid, summary, longdesc, revised, startdate, duedate, resolveddate, closeddate, issuerisklevelid, userdata1, userdata2, userdata3, percentcomplete, estimatedays, estimatehours, estimateminutes, visibility, visibilitymembertype, parentissueid, originatortype, originatorreply, originatordata, originatorprocessed) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?); select SCOPE_IDENTITY()] at NHibernate.Id.Insert.AbstractReturningDelegate.PerformInsert(SqlCommandInfo insertSQL, ISessionImplementor session, IBinder binder) at NHibernate.Persister.Entity.AbstractEntityPersister.Insert(Object[] fields, Boolean[] notNull, SqlCommandInfo sql, Object obj, ISessionImplementor session) at NHibernate.Persister.Entity.AbstractEntityPersister.Insert(Object[] fields, Object obj, ISessionImplementor session) at NHibernate.Action.EntityIdentityInsertAction.Execute() at NHibernate.Engine.ActionQueue.Execute(IExecutable executable) at NHibernate.Event.Default.AbstractSaveEventListener.PerformSaveOrReplicate(Object entity, EntityKey key, IEntityPersister persister, Boolean useIdentityColumn, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.AbstractSaveEventListener.PerformSave(Object entity, Object id, IEntityPersister persister, Boolean useIdentityColumn, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.AbstractSaveEventListener.SaveWithGeneratedId(Object entity, String entityName, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.EntityIsTransient(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.PerformSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.OnSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.FireSave(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.Save(Object obj) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558, Boolean x8b15d0e18e6888d9, ISession x45b53be31e53d68b) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558, Boolean x8b15d0e18e6888d9) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558) at CounterSoft.Gemini.DataProvider.xc0186e148e957052.x0dd7228622330700(IssueEN x22c77d60925997e9) at CounterSoft.Gemini.Business.x95da312ae9372c2e.x0dd7228622330700(IssueEN x22c77d60925997e9) at CounterSoft.Gemini.Presenter.IssuePresenter.CreateIssue(IssueEN issue) at CounterSoft.Gemini.Web.Api.IssuesRestHandler.IssueCreate(RequestDetails rd)
42 26/03/2010 15:31:06 Error Gemini could not insert: [CounterSoft.Gemini.Commons.Entity.IssueBareEN][SQL: INSERT INTO gemini_issues (projectid, issuetypeid, issuepriorityid, issueseverityid, issuestatusid, issueresolutionid, reportedby, fixedinversionid, summary, longdesc, revised, startdate, duedate, resolveddate, closeddate, issuerisklevelid, userdata1, userdata2, userdata3, percentcomplete, estimatedays, estimatehours, estimateminutes, visibility, visibilitymembertype, parentissueid, originatortype, originatorreply, originatordata, originatorprocessed) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?); select SCOPE_IDENTITY()] at NHibernate.Id.Insert.AbstractReturningDelegate.PerformInsert(SqlCommandInfo insertSQL, ISessionImplementor session, IBinder binder) at NHibernate.Persister.Entity.AbstractEntityPersister.Insert(Object[] fields, Boolean[] notNull, SqlCommandInfo sql, Object obj, ISessionImplementor session) at NHibernate.Persister.Entity.AbstractEntityPersister.Insert(Object[] fields, Object obj, ISessionImplementor session) at NHibernate.Action.EntityIdentityInsertAction.Execute() at NHibernate.Engine.ActionQueue.Execute(IExecutable executable) at NHibernate.Event.Default.AbstractSaveEventListener.PerformSaveOrReplicate(Object entity, EntityKey key, IEntityPersister persister, Boolean useIdentityColumn, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.AbstractSaveEventListener.PerformSave(Object entity, Object id, IEntityPersister persister, Boolean useIdentityColumn, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.AbstractSaveEventListener.SaveWithGeneratedId(Object entity, String entityName, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.EntityIsTransient(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.PerformSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.OnSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.FireSave(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.Save(Object obj) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558, Boolean x8b15d0e18e6888d9, ISession x45b53be31e53d68b) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558, Boolean x8b15d0e18e6888d9) at CounterSoft.Gemini.DataProvider.x73a34067f4cd229a.xf606eb5e1032d933(BaseEN x6fcb9c1c812a0558) at CounterSoft.Gemini.DataProvider.xc0186e148e957052.x0dd7228622330700(IssueEN x22c77d60925997e9) at CounterSoft.Gemini.Business.x95da312ae9372c2e.x0dd7228622330700(IssueEN x22c77d60925997e9) at CounterSoft.Gemini.Presenter.IssuePresenter.CreateIssue(IssueEN issue) at CounterSoft.Gemini.Web.Api.IssuesRestHandler.IssueCreate(RequestDetails rd)
41 26/03/2010 15:31:06 Error Gemini Exception has been thrown by the target of an invocation. at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at CounterSoft.Gemini.Web.Api.RestHandler.GetResponse(RequestDetails rd, MethodInfo method)

This is because one of the values (issue priority, status, type, severity or resolution) is invalid.
Please make sure that the ids are valid.

OK that run.

You must also ensure that the 'summary' and 'long description' are specified. I tried to create an issue with just the summary and got the same error.