Creation of Exchange 2000 Mailboxes

Sir,

I am trying to create exchange mail boxes for my users but when I right click a user and create a mail box using exchange tasks it tells me that the mail box has been successfully created but in actual the mail fail is not created and any attempt to send mail to that particular user fails.

I checked on the Microsoftr web site they say this is an issue with the Exchange Service Pack 3 but till present I do not know of any fix or patch to solve this problem

This problem is fairly urgent and a quick reply would realy be appreciated