As you can't create a backup, I would recommend choosing File | Save As... and save a copy of your file with a slightly different name (Smith1.paf instead of Smith.paf for example), (this is so you have a "backup" of the file) then try the following:
Click on File | Check/Repair... then on the Check/Repair button. Do this a couple of times. If the errors stay the same and are not successfully repaired, the next step would be to try exporting your file as a GEDCOM (click on File | Export... then on the Export... button, set the save in location as My Documents, and name your file and click on Export.
Next create a new, empty database, and import the GEDCOM you just created into it. (Click on File | Close until all open databases are closed, then click on File | Import and follow the on-screen directions)
If this does not solve the problem, you can contact PAF support in Salt Lake City via email at: firstname.lastname@example.org