revit 8.0 - can't open project files

[jackson.144483]

Hi All, Our company recently did a server upgrade and from that day onwards any project file that we try to open crashes revit (that "an unrecoverable error has occured" message comes up) and closes the program. The strange thing is all template files still work fine, also if we copy the file to a local folder (anywhere on C:/) the files will open fine. We were told it would be the anti-virus software we are running and that all we had to do was set revit up as an exception to the software and it would work. We tried this and are still having the same problems. Has anyone ever experienced this or something similar and any idea how to fix it?

Thanks
Jackson