actually i would refer to post 29 of this thread http://howtoforge.com/forums/showpos...6&postcount=29
WARNING: I give no support for the correction of the post!
What I can remember, the problem is when you created a mailbox and it got linked to a sys_user which isn't associated with a client id.
PS: When you still don't have a solution, write me a pm with your contact details, gtalk, msn, icq, etc. whatever you like.