I would have to see more about what packages you are using, etc, to even guess, but I would suggest dumping totem.
www.xine.org and a lot of people like mplayer (esp those who love Apple Quick time format).. Make sure with xine you install the libdvdcss or whatever (on the bottom of the download page) or DVDs wont play...
Thats illegal in some countries so make sure you check with your local mafia first.