Thanks for replying, Lakshman.
I have already tried to turn off ProtectedMode. Same bug. Using the latest 4.7.3.
We used a clean VM Windows 7 32-bit for the build. The WOW64 line is automatically commented out.
Like other posters, I too believe that this is some weird sandbox issue that is causing Firefox to believe the profile data is corrupted because of the sandboxed Flash plug-in.