Here's the situation. You check your application logs and notice you have 2000 errors with event id 8331. You read further and it says that a service threw an unexpected exception which was caught at f:\Titanium\Dsa\Src\Lra\Abv_dg\Lservagent.cpp(4511)

You then realize that you dont even have an f:\ drive. You are now in the vortex of yet another MS bug. You may also notice that the Active Directory updates from Exchange 2003 are no longer working correctly.

The cause is related to a bug in Recipient Update Services. To temporarily fix the problem you can either restart the Exchange Attendent Service or reboot the server.

After a long wait MS finally relized that this was a problem and have included it in the begged-for Rollup patch located here.