iTunes 10.5 cutting off music?

I've recently purchased a new Macbook Air and I love it except for a minor issue.

I have migrated from a PC to Mac and everything has gone smoothly so far when setting up iTunes. I had my music library on an external hard drive that was originally hoooked up to my desktop PC. However, this hard drive is not very practical when it comes to portability. So, I purchased a new WD My Passport for Mac. I hooked them both up and transferred all my media from the old drive to the new one. I then imported all the media into my iTunes and chose the new external drive as my download location for new purchases.

However, I have noticed that a couple songs (I haven't listened to all 1100+ songs yet) are cut off. And not just a couple seconds at the end of the song. It's anywhere from 50s - 1 min at the end of the song that is cut off. The song continues to play, but with "dead air". This happens when playing the song from iTunes or my iPod/iPhone.

Today I deleted the songs from the new external hard drive, then hooked up the old one and re-copied them to their directories. I still have the same issue. The interesting thing is that if I play the songs in QuickTime I have no problems. They play through entirely without cutting off. No "dead air".

I'm at a loss as to what this issue could be. I am running iTunes 10.5 (the latest one) and iOS 5 for both my iPod Touch and iPhone. Mac OS X (10.7.2), 13 inch i5 Macbook Air. Any help is appreciated in advance. Thank you for your time and efforts.