If It Wasn't Tragic It Would Be Funny
Exchange 2007 has a leap year bug.
No more information than that, really; but under certain configurations, Exchange is generating:
Event ID: 2451
Source: MSExchange ADAccess
Type: Warning
Description:
"Process powershell.exe (EMS) (PID=1250). Contacting server fqdn.of.mailbox.server.example.com for RUS RPC service returned RPCException 'Error 6ba from FilterAttributes". Server will not be used for RUS RPC.
and not processing any user creations or recipient updates.
Let's just hope it disappears at midnight tonight...