Project Server 2007: Timesheet gets an unexpected error has occurred when opening

I get an error message when opening all timesheets of one user under PWA (project server 2007): An unexpected error has occurred

By enabling details in web.config, I get the following error:

 

Server Error in ‘/’ Application.
——————————————————————————–

Specified cast is not valid.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidCastException: Specified cast is not valid.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. 

Stack Trace:

[InvalidCastException: Specified cast is not valid.]
   Microsoft.Office.Project.PWA.WebParts.TimesheetPart.LoadTimesheetData(GetTSDataModeEnum LoadingMode, Guid resUID, Guid prdUID, Navigation ps) +16703
   Microsoft.Office.Project.PWA.WebParts.TimesheetPart.OnLoad(EventArgs e) +2993
   System.Web.UI.Control.LoadRecursive() +66
   System.Web.UI.Control.LoadRecursive() +191
   System.Web.UI.Control.LoadRecursive() +191
   System.Web.UI.Control.LoadRecursive() +191
   System.Web.UI.Control.LoadRecursive() +191
   System.Web.UI.Control.LoadRecursive() +191
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2428

 

——————————————————————————–
Version Information: Microsoft .NET Framework Version:2.0.50727.4200; ASP.NET Version:2.0.50727.4016

 

Then, I don’t know how to find out the error. Please help.

 

Hello Maxsteak,I looks like somebody was in the web.config and fat fingered a character.Restore the web.config from a previous backup.CheersMichael Wharton, MBA, PMP, MCT/

Dear Michael, Thank you for your feed-back. I’m not sure to understand your point since I changed the web.config after the user informed me about the real issue (based on this article which is similar but cannot solve my case: http://www.epmfaq.com/ssanderlin/project-server-2007/looking-behind-an-unexpected-error-has-occurred-messages

Hello Maxsteak,This problem could be caused by the fact that the user has modified the Timesheet page in the Personal View. To see if the user has the rights to do so: go to the PWA home page, click on the user name in the top right of the web browser and see if the user