Did you remove PAF before reinstalling it? In my experience, removing the old install is essential to getting rid of corrupted settings. It will not delete your PAF data files, but keep a copy on removeable media in any case.
Hmm ... I was contacted a few days ago by someone who said that the PAF setup program he had recently downloaded would not install on his 64-bit Windows7. I sent him a copy of the setup program that installed correctly. If you would like, I can send you a copy of the same setup program I sent him, if you contact me privately at email@example.com
Another thing to check is Tools menu > Preferences > Folders, to make sure that you have not specified a non-existent location for your backups. If so, it is easily changed by deleting the location or leaving it blank.