So you went ahead and installed Windows Server 2003 Service Pack 2 on your Exchange 2003 cluster because it’s a “good thing” (Not that service packs are not good things, they really are!).
Everything went well until all of a sudden, your users report that they can’t access their mailboxes through OWA. They complain that they get the dreaded “500 – Internal Server Error” message in their browsers.
And then… you should find your problems melting away.