After doing a Windows Updates, I received a permanent message at the bottom right corner saying my version of Windows 7 is invald. When I entered the product key that came with my computer, it wouldn't accept it.
I restored my system to an earlier backup and the problem went away. I've been using the same product key since 2009 without any problems.
I suspect the problem lies in one of the recent October 8, 2013 updates since others seem to be having the same problem. After I did the restore, I only updated my Office 2007 and the .NET updates. I didn't install any of the others because obviously
one or all of them are the problem. The updates I didn't install are:
Security Update for Windows 7 for x64-based Systems:
KB2862335, KB2864058, KB2864202, KB2868038, KB2876284, KB2883150, KB2884256, KB2847311, KB2862330
Update for Windows 7 for x64-based Systems:
KB2846960, KB2852386, KB2882822, KB2888049
The clear solution to me is to not install any of these updates from October 8.