insert any DVD movie...system CRASHES!!

when i insert a dvd movie the blue screen pops up saying something like
"Error....trying to run a thread that is not owned." then my system
crashes.??? i'm no computer guru so i have no idea. anyone? all my drivers
are up to date, all other ways of using media player work (even the
pre-installed videos). i have a geforce 8800 gts 640mg so my card can
handle a lot......oh, and i can play dvd rom games fine just not dvd movies.
all media options are the default too. and i built the computer with an amd
x2 64 6000+ 3ghz. why oh why......????

thanks,

chris