0:00 MP3 Problem?

I currently have about 72 mp3s in my collection that are (for some reason) reading as 0:00 in length. They play fine in Winamp, but iTunes won’t even accept that they exist. Any way to easily correct all of these without burning a CD and re-ripping them all? If I open and re-encode them it seems to work fine (with Audacity) but if there’s a simpler way I’d rather do that!