I found my answer in another post...
"cbs604 (Instructor) Apr 1, 2004
Well, here's what happened: The owner didn't tell me until today that this problem started after he had his mother board changed. Turned out that whoever put the computer back together again didn't update the system date, which was set to May 2003. So all the messages that went out in this last week have vanished, but were delivered OK.
By setting up the correct system date, all is now well, but the mystery remains - what happened to those sent messages?
Cheers,
Brodie"
Thanks again Brodie