A lot of Exchange administrators that restarted their Exchange servers on 29th February this year, ended in endless research of discovering why they can't create mailboxes, enable mailboxes or even start Exchange setup.
The problem was not in network or any other service but in Exchange 2007 server's bug.
Nino Bilic from Exchange's team wrote on the team's blog:
After investigation of this problem we have learned that this problem would occur only if you have started or restarted the Microsoft Exchange System Attendant service between 12:00AM UTC , Feb 29, 2008 and 12:00AM UTC, Mar 1, 2008. It is important to note that the times involved are UTC, not local server time.
You can sleep in peace for at least 4 years :))))