I've noticed some weird things in WMP 8 under Windows XP. First of all, some of the MPG movies I play will freeze if I try to adjust any of the video settings (brightness, contrast, etc.). This happens with some but not all MPGs and not with any other type of movie file (ASF, AVI, WMV, etc.).
Also I've noticed that WMP 8 often cuts off the very beginning of movie files and mp3s when I play them.