Weird media streaming issues

I just finished building a new rig, everything boots fine and things seemed to be working swell. I was able to download big files, surf the web, play Combat Arms, etc. no problem.

I just tried to stream some video on hulu, and after a minute or so, the video gets really choppy. the sound will keep going on fine, but then everything starts getting really laggy. even after i exit full screen mode, or even if i close down firefox, if i try to click on any menu or window, it takes several seconds for the menu/window to show up or minimize. the only thing that helps restore things to normal is rebooting. so far this has only happened while streaming from hulu.com. i have the most recent drivers for my video card installed, and like i said, it seems to run games fine. any suggestions?

system specs:
AMD phenom II x3 720
4gb ddr2 800mhz
sapphire ati radeon hd 4850 512mb
gigabyte ga-ma790x-ud4p mobo
windows 7 RC 64-bit
netgear wn311t wireless adapter
res: 1920x1080