WMP11 Not Playing Mp3 Files

I'm running Vista Ultimate x64 and noticed a problem recently when playing music via windows media center. However, having played around in WMP11 also, WMP is doing the same thing so I believe the problem is somewhere in there. Initially the problem started when trying to play a collection of mp3 files off my local drive. Whether it be via an existing playlist or simply by selecting an album within WMC. The problem is that a track plays and then WMC/WMP freezes on the next track. If I skip to the next track that plays, but then the next track freezes. Sometimes the 1st track on the list doesn't play but the next will. Sometimes the 1st plays and then the next won't!
So, I closed WMC and opened up WMP directly. (This happens in both x86 and x64 versions of WMP by the way). If I create a playlist, the same thing happens a track plays, then freezes, if I skip on, the next track plays and then the next one freezes.....