gf4mx440 black screens when using explorer to browse hard drive

I'm having this weird problem with a gf4 mx440 64mb ddr in that when ever i
single click on an mpg file or any movie for that matter in windows explorer
my screen goes black for a few seconds then returns as if nothing has
happened my guess is its a full screen video overlay problem but i have
turned this off in my display properties. my friend has the 128mb version of
my card and it exhibits the exact same symptoms the weird thing is it has
only just started doing it in the last 2 weeks but i have been adding
software and updated drivers so i am not sure how the problem has occurred.



I have just started using the pc as a digital video editing platform for my
DV home movies, so its happening loads now as i compile clips from my hard
disk



It looks as though while exploring the drive my computer is trying to
generate a thumbnail of each video clip but it is going to a full screen
overlay while it looks for the first frame?



athlon 2000

gigabyte ga7vaxp

512mb ddr ram

windows XP pro