Global Catalog and Exchange server

Hi folks,

I have two 2003 DC's that are also GC's. The problem is that if I take the first one offline, the Exchange 2000 server doesn't see the second one, therefore people can't access their Outlook email accounts anymore. The second DC is in a different subnet. I checked to see if they are both setup as GC and it looks fine. If I check the Directory Access in the Exchange server, both GC's show up. What could be the problem?

Any help would be appreciated.