I have 2 domain controllers in the same physical location as my Exchange server and all in the same AD site. The Exchange server is automatically configured for DSAccess and is using the 2003 server. I didn't know why it doesn't show the 2008 server so I added manually for redundancy. However, when running ExBPA, it says it can't use that server because it's not functional.
I have looked at the 2008 server and AD appears fine. It is configured as a GC and I verified the gc srv dns records are present. Why else would it not work?