It might be your GF4, I don't know... mine seems to work just fine (ti4200 as well, from MSI), so it's definitely a possibility. Do you happen to have any other systems you could try the GF4 in (you'd obviously want to keep the same OS and kernel, as much as is possible)?
Were you running the same version kernel on your old motherboard? Might be worth a shot (your old motherboard, this kernel, and the GF4), if it's not too hard to get set up.
I don't know of anything it might be, but I'm trying to at least narrow things down. At this point, it seems to be either your GF4 itself, or some motherboard feature that it enables that's buggy or unsupported in that kernel.