animations deside to not work

[slickmasterizzy]

when i start up the game everything runs fine, but after 5-20minutes all animations just stop. i move by sliding and all NPCs that walk around are still frames that just move around. just lately maybe 5 minutes after this happens my character will just start moving insanely fast for no reason, i like to group and this is really annoying to other people and me. any idea whats up?

dv9700 hp laptop
2k ram
direct x 10
geforce 7150m

its really weird because i dont get any lag, so i dont understand what the problem could be.
by the way im running Vista

Thanks