can't play video

[theboytony]

whenever i try and play a video file, whether it is dvd or avi the file starts playing but the screen goes multicoloured and blocky so i can't see anything. i've tried in movie player and vlc but its the same with both, can someone please help. i am using ubuntu 8.1 on a dell inspiron 6400

thanks

[taurus]

Do you have compiz running?

[theboytony]

not anymore had to turn it off when i installed xbmc, but that works anyway so just gonna use that instead