Assuming you are in a region where you are allowed to redownload your past music purchases, delete the corrupt tracks from the music section of your iTunes library, close & then reopen iTunes, go to the iTunes Store home page, click the Purchased link from the Quick Links section in the right-hand column, then select Music and Not on this computer. You should find download links for your tracks there.
While downloading select Downloads in the left-hand column and make sure Allow Simultaneous Downloads is unchecked.
If the problem persists, or that facility is not yet available in your region, contact the iTunes Store support staff through the "Report a problem" links in your account history, or via Contact Support.
Oh **** no. Now it's obvious whats going on. These files AREN'T corrupt anywhere save iTunes. They play fine in ANY OTHER MP3 player. It's obvious that this is a money grubbing scheme, Apple doesn't fix this because theres no money to be made in making a broken CD work, but as we all recall there sure is more money in replacing your scratched CD's! SHAME ON YOU APPLE.
I had a problem - AAC protected songs I purchased back in 2006-2008 timeframe where being cut short, truncated, when played back. The file size and duration where not affected. It occurred when I copied the files to a backup external drive and then tried to copy them back to the local drive.
Solution: From itunes, I when to the "Show in Windows Explorer" selection, then I right clicked on the file name and selected "rename" Even thought I could not see the three character extension from that screenm I just added .m4a be sure to include the dot. This changed the true file name to be songname.m4a instead of songname.m4p which is what the protected ones were. Best of luck.