Just so you guys are aware of this:

http://support.microsoft.com/kb/970269

This is exactly the problem we're having with the 64-bit version of ClearCanvas Workstation.  This hotfix has solved the problem for us (we updated the SQL CE DLLs in "ReferencedAssemblies\SQLCE\x64" with these).

I believe SQL CE 3.5 SP2 is due out shortly, and presumably it addressed this issue.  Anyway, I figure you guys will move to SP2 when it's out, but, if you're not, or you consider it low priority, you might want to reconsider.  It's a pretty serious problem that basically just shuts down the application when you try to open a study.

Wes