Not sure. It's not something I've seen elsewhere. There aren't any huge, general, performance improvements between 2005 & 2008, but there are no huge performance degradations that I've seen either. I have seen queries that performed worse between the two, but those were almost always edge case queries anyway. Most ORM queries that I've seen wouldn't qualify (not all, there are a few doozies there) since they're overly simplistic frequently, not overly complex.

This is a bit of a stumper. What about connection pooling? Is it disabled/enabled on either of the servers different from the other?