Itunes won't play mp3's?

My iTunes was working fine on my computer, but all of a sudden, the MPEG Audio Format files aren't working. It seems as if they are speeding up during playback, playing many times they're normal speed (a minute and a half song will play in about 15 seconds), and they are not playing correctly. I've tried everything to get them to work correctly, but they aren't. Does anyone have the same problem or know how to fix it? The AAC, WAV, and Quicktime files are playing fine. It's just the MPEGs...Thanks!