I think this has something to do with artwork.
For those of you scouring 1000's of tracks looking for faulty ones, try this:
go to the iTunes folder in your folder system and look in the 'iTunes Music' folder, where all the mp3s etc are stored.
Open up the indiviual folders for the albums to see the list of mp3s / songs for that album. If they are saved in itunes with their artwork, then you will see that the individual music files are listed with a thumbnail sized picture of the artwork as the file icon, rather than the standard apple mp3 icon.
I have found that for corrupted mp3s, the songs that should have the artwork icon, instead just have the standard apple mp3 icon. It also tends to be not all the tracks in an album, but only the final half of them, for some reason.
This might make it easier and quicker to idetify, at a glance, what songs are affected. I've also found that when I import mp3s from a CD, everything is fine, all songs are working until I add the artwork. Then they become corrupted.
Once again, I only use mp3s, never the ACC itunes format, I have never used Match, and I have up to date versions of software running on snow leopard. I think this is a wider problem with itunes, not just with match.
Does anyone out there find this information useful??