will the file play in anything else?
I've not tried xmms with anything other than mp3's and oggs, because I've always used xine (my personal favourite) or mplayer (the kmplayer front end to mplayer is pretty good).
http://dag.wieers.com/packages/smpeg/ ( a small mpeg player )
Worth browsing this site (if you don't already know it) there's a fair bit of stuff for Fedora.