Try this Microsoft fix:
http://support.microsoft.com/default.aspx/kb/941090
Incidentally, although it only mentions 'outbox', it works for all folders.
--
Gary VanderMolen, MS-MVP (WLMail)
"Tony" <Tony@xxxxxx> wrote in message news:CFDCA247-C247-4344-B0BB-7673F2204018@xxxxxx
Quote:
>I got 1 email stuck in the outbook:
>
> (1) it has been sent and can be found in "SENT" box,
> (2) but it still appear in "OUTBOX" and cannot be deleted (I tried many
> times and said "unknown error:",
>
> Now I cannot send other emails. All outgoing emails are stuck in the
> "OUTBOX". Could someone help with this? Thank you.