DATA FILE IS CORRUPT AND NEEDS TO BE MANUALLY RECOVERED
This is possibly a bug in Revit 2012.
Solution in the Autodesk Knowledge base article:
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=17680194&linkID=9243099
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, open Windows Explorer (Windows key+E), enter "%TEMP%", then in that folder delete as many files as you can.