As a follow-up; I have checked this error all over the web. A bit nuts trying to find a solution. SW lists it as file corruption in most cases. All files worked fine in 2010 a few days ago, so this seems unlikely.
We're experiencing the same issue with Solidworks 2012. Parts and Assembly's are created by a Template. All files are saved on a Windows 2008 server.
We haven't found a solution yet, you?
No, although it has resolved itself on my SW2010 files. Have no clue why, but suspect this is an OS issue and may have been resolved through an update.
I am however stunned at how buggy my 2012 is next to 2010. Menu issues, odd crashes, photo360 issues. On and on. A bit let-down to be honest.