Can you please check to see if the project.aspx file exist under the Project directory of the Gemini site?
How did you install Gemini?

Yes it does.

I installed Gemini from the .exe file.  I installed it as a virtual directory http://<IP.28>/Gemini

But then I created a new virtual directory under Default Web Site http://<IP.247>/Gemini and point the home directory to the path where http://IP.28/Gemini pointed to before. 

Then I removed the path from http://IP.28/Gemini


I can go to RoadMap link from Gemini home page fine, but clicking on any existing issue on the RoadMap page, I got similiar error:

Server Error in '/Gemini' Application.

        <h2> <i>The resource cannot be found.</i> </h2></span>

        <font face="Arial, Helvetica, Geneva, SunSans-Regular, sans-serif ">

        <b> Description: </b>HTTP 404. The resource you are looking 

for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable.  Please review the following URL and make sure that it is spelled correctly.

        <b> Requested URL: </b>/gemini/issue/ViewIssue.aspx<br></font><br><br>

is this the only page that is causing issues? Which version of IIS?

IIS 7 windows 2008

When i clicked on My Watches, and then click on the issue on My Watches page, i got similiar error too:

Server Error in '/Gemini' Application.

        <h2> <i>The resource cannot be found.</i> </h2></span>

        <font face="Arial, Helvetica, Geneva, SunSans-Regular, sans-serif ">

        <b> Description: </b>HTTP 404. The resource you are looking 

for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable.  Please review the following URL and make sure that it is spelled correctly.

        <b> Requested URL: </b>/gemini/issue/ViewIssue.aspx<br></font><br>

I think i found the problem.  I put back the path in http://<IP.28>/Gemini and browse the Gemini from there, I have no problem viewing the issues via RoadMap page or MyWatches page.

i think i fixed the problem.  Because when I switched the virtual directory from one IP to another.  I did not update the Full Gemini URL in Global Settings -> General to use the new URL before disabling the old URL.  So, some features don't use full Gemini URL, but some do such as: view issue from RoadMap page, My Watches page, and clicking on RoadMap from drop down of project title/name