You didn't mention if you had any 3rd-party extensions, if so try removing those
Might be a corrupt registry key. Check in
HKEY_CURRENT_USER/Software/FileMaker/FileMaker Pro Advanced/<xx>/Preferences
where <xx> is the version
If you uninstall all versions of FMPA you could check and see what keys are left in that area and remove them.
Registry editing is dangerous and is at your own risk so if you're not comfortable don't do it.