some XviD builds have problems decoding or recognizing some XviD files as actually being XviD files.. e.g. XviD [Nic's build 16/03/2003] had problems playing two xvid movies. After replacing it with XviD Decoder [Koepi's build 04/10/2002], everything went fine. Try K-Lite codec pack 2.02 (_not_ 2.01), at
www.k-lite.tk.