hm, i don't know anything certain, but best way first is to update your drivers. nothing else is so effective like doing this
when this don't work, ehm, try to reinstall and when everything went wrong, then go and defragment your hdd, perhaps files are little bit too cutten, i think so....
gr€€tz
cYbErB00M
ps: i'm from switzerland, so you know now why my english is not the best one...