Easy answer: "Gerrymandering".
North Carolina is a Democrat state, both houses being Democrat. However, both houses flipped this year to GOP for the first time since Reconstruction. They get to draw the districts this time around.
I suspect we'll see a few more Republicans from North Carolina in 2012 when they get the current "solid Democrat" lines straightened out.
The GOP will make sure that Heath Schuler and surviving Blue Dog Dems are pushed into unfriendly territory. Kiss em good bye in 2012..