'The messaging interface has returned an unknown error-if the problem persists, restart Outlook'

[Tim Colling]

Hi -

I am running Outlook 2002, SP-2, under Windows XP Home edition, SP-1. I use
MS Word as my message editor.

For the past few months, I get the following error message in a dialog from
Outlook:
'The messaging interface has returned an unknown error-if the problem
persists, restart Outlook'

This occurs when I either create a new message or note or edit an existing
message or note and then leave it open for more than just a minute or two,
rather than closing or saving and closing it.

I have run the "Detect and Repair" menu option in Outlook several times, but
that has not solved the problem.

My outlook.pst file is under 500 MB in size, and my archive.pst file is
under 400 MB in size.

I also have MS ActiveSync 3.6 installed. This problem arises regardless of
whether I am running ActiveSync 3.5, 3.6, or 3.7 running - I have tried
installing them all, and I can reproduce the problem with any one of those
versions running. The problem did not occur before I installed ActiveSync,
but it did not manifest itself until I had been using ActiveSync for a few
months, so I speculate that it is not related to ActiveSync, but I am not
certain about that.

Can anyone suggest a solution to this problem?

Thanks,
Tim