Corrupt Revit Project File

This was written by Chris Aquino, The Revit Clinic...

"We (Autodesk) have started to see a few more of these types of cases, and a new Knowledge Base document has been created to organize some of the options for this scenario:
Data file is corrupt and needs to be manually recovered
Update: If this message is only happening on one machine. Try freeing up some space on the hard drive, as well as clearing out the TEMP folder on the machine. To find the TEMP folder, hit Windows+R, enter %TEMP%, then delete as many files as you can"