There are some discussions in the Apple support forums, about this issue (problems when playing PAL material on the new ATV2).
I am in the same boat, I am traveling to US next week and wanted to buy a ATV2 for the wife, she loves downloading films from a Russian site (she is Ukrainian). Until now, she watches them on my iMac, it would be nice if she could watch them on our TV. But I am afraid that since the material is PAL (probably?! I am not an expert on these things) it will not play well with ATV2.
I need to check out TV specs if it can play @ 60 Hz which is the standard ATV2 seems to understand.