Quicker than filling out text in a field, this is what I tried, though mind you, I never rate my music. This might not work for those that rate their music.

The exclamations only showed up on a few seemingly random songs. out of 100GB this was a lot to sort.

I dragged my music folder into itunes, automatically finding the missing songs.

At this point I had duplicates, the old ones with exclamations, and the new ones that worked just fine.

Go click on "show duplicates" then give all your duplicates a rating. (this goes WAY faster than changing text in a field)

ONLY your duplicate files will be affected, and all you have to do now is sort by rating.

The exclamations will be without a rating, and the good files you want to keep will have whatever rating you set.

Remove the afflicted files and you're good to go.

Took me ten minutes TOPS doing it this way.