<P ID="edit" class=small>(Edited by Claude on 05-Mar-05 12:58. insert a clickable URL)</P>After a hard drive crash and subsequent replacement, I replaced the PST file from the image off the previous drive. This file was so large [1.9 GB] that it caused Outlook to stall.
Outlook would open, seem normal, but would not download messages[not enough space to store them]. When this was happening while I had a message in the Outbox, each time the send/receive failed, the outgoing message would actually send, but it would not be moved from the Outbox to Sent Items. This led to unknowingly sending multiple duplicate messages.
I fixed all of this by going to the Archives of Woody's Office for Mere Mortals, v3-n17, and followed the procedure in Section 4 for a "Born Again" PST.
Problem Solved.