Yes bones rotation have to be 0.0.0. to be able to be in a Bind pose.

However, in 2k8 you can have multiple bind poses, so this means they will not be on 0.0.0.

I have not gotten the opportunity to test this out, so i might be very wrong about this now.

So it could be that its your rotated bone, or the constraints, maybe try to go back and undo it, and make a small export test.