Welcome to the forum.
It sounds like PrE is missing the PAR (Pixel Aspect Ratio) flags in the AV file. If in the correct Project, one should be able to use Interpret Footage to "force" PrE to see that PAR (1.212), and correct the pillar box effect.
What camera did the footage come from, and did you Capture in PrE via FireWire, or did you Import that footage?
Thank you so much! I changed it to interpret it correctly and now it looks normal.
Great news. With some footage, PrE can miss the flags. Usually, it is the recording device taking a few liberties with those flags, but sometimes it seems that PrE just misses them. Players, and other programs, seem to see them OK. In those cases, Interpret Footage will force PrE (or PrPro) to treat that footage, as it should be.
Good luck, and thanks for reporting your success!