You have 2 options:

1. Use security scheme per project. That way you assign permissions to that projet only (eg view project, Assignable to issues etc..)
2. Use one security scheme and use project groups (assign permissions). With project groups you associate user on a project basis. So if a user is in group X for project A he will not be a member of the group for other projects.

Thanx for the quick reply. But what about the Global groups? Do I need to use those aswell. Because Global groups are connected to project automatically and seem to overrule the settings at project group level

If you are not using global group simply remove those from the security scheme.
If a user is a member of global group G and project group P for project X then he will have the combined permissions that group G and P has.

OK. I have created one security scheme, removed all global groups on this scheme and added the related project groups. Next problem: creating an issue is not working. After saving the issue the window returns to the issue create page. Is there some other option I have not set correct within the administration?

It is probably due to required fields not being populated. Did you set default values for the project (Project Administration -> Default Values)?
Also, check Gemini's system log.

System log shows the following error: User Perry Stinis does not have permission for: view project. at CounterSoft.Gemini.Presenter.Base.BasePresenter.HandlePermissionException(String operation) at CounterSoft.Gemini.Presenter.ProjectPresenter.GetComponent(Int32 projectId, Int32 componentId) at CounterSoft.Gemini.Web.Methods.ComponentMethodHandler.GetComponent(Int32 componentId, Boolean writeResponse)

Permissions for this user/project:

Permissions

Managers

Project Project Group Membership Permissions www.interimpuls.nl development Project Leads Administer Project View Project Assignable To Issues View Documents Manage Documents View Schedule Manage Schedule Administer Issues Create Issue Edit Issue Batch Edit Issues Delete Issue Assign Resource Assign Version Set Issue Visibility Close Issues Resolve Issues Link Issue Move\Copy Issue Create Comment Edit Comment Mark Closing Comment Delete Comment Set Issue Watchers View Time Logs\Reports Log Time Manage Time Logs View Issue Watchers and Voters Only View Own Issues

What is the missing setting?

It is not a permission issue. Which fields are shown when you are creating an issue?

When I create an issue I see the following fields: - Projects - Issue title - Detailled description - Visibility - Fixed in version - Assigned resource - Work estimate - Reported by - Attachment

Please make sure that you have setup project defaults for component as it is a required field (Project Administration -> Default Values).

That seems to be a solution. Finally managed to create an issue. Thanx for the support