why is there digital slur sound from youtube/google vids?

[excellsior]

ok i have a fresh computer, formatted yesterday, updates etc, plugins for firefox
msi k8ngm2 fid mobo + creative xfi xtrememusic. plays mp3s fine and some mov files and wma/wmv files, but some of my video clips have distorted sound. and everysingle youtube/google vid has distorted sound as well. not sure whats going on.

 

[excellsior]

i have to reinstall drivers each time and restart to have it work. but it goes bunk after a while.

also some of my mp3s are being played messed up as in the vocals fluxuate in volume and sometimes i cant hear what theyre saying.

bass is the only thing that seems to always be working in youtube and mp3s.

not sure if its my software or hardware.
i have the xfi xtreme and k lite codec package installed. i think theres some audio tweak device but i havent touched it.