Hello! I believe I am having the same problem you all are having.
I can play SC:BW for HOURS, or, maybe only for five minutes, and then my screen jars and I get this disgusting freeze that is impossible to escape from, no alt-tabs, no alt f4's, no nothing. It almost seems like a hardware crash.
I believe I am a little closer to the solutions, though, than most...
I had Windows XP SP2 x86, and I was having these problems. Well, I upgraded from XP SP2 to Windows 7 x64. A COMPLETELY new OS with a different architecture (32 to 64bit).
I STILL have these problems!
I believe that means it -MUST- be hardware related, there's no way around it! ALSO...One of times my computer screen froze, I hard-rebooted and then my monitor had a bunch of weird numbers/characters on it - my graphics card got fried!
One GFX later, I'm still having the same problems!
What kind of mobo are you guys using? I have a P5N-E SLI ASUS board.
My AIM name is Wing Neo Star 15, maybe it'd be easier to talk there, otherwise respond here if you have any good info!