Weird Video Playback Problems

Hi all,i use ubuntu 7.10. i'm very happy with it but off late i have this weird problem. The Video playback gets Black and white all of a sudden and once it is that way it remains that way only. The only remedy to this is that i have to make a new account and then view the same video again. It works fine!!!!! i'm pretty new to ubuntu and i am just a  basic user. Can anybody help i have installed gstreamer plugins ( all non-free codecs too). even the audio visualisation in totem or  vlc gets  black and white.....

reiteration

i am having the same problem with video in totem, vlc, and beep. i too am new to ubuntu and have no idea how the video can be corrected. i dont think its a codec problem either because i have tried avi, mpg, and mov; all of which are black & white (although the videos' thumbnails show up in color). moreover, ive been having graphics problems generally that might be tied to this. both f-spot and gimp are running with major latency problems. thanks, mfg