Lost Sent Items

I have a user who reported a strange problem.

She is missing e-mail from her SENT ITEMS folder. The
range is from some time in 2003 to some time in 2004.
She has sent items from before, and after that time
period. She simply seems to be missing all emails from
that particular date range.

Autoarchive Settings:
Run Autoarchive every 14 days - checked
Prompt before autoarchive runs - checked
Delete Expired items - checked
archive or delete old items - checked
show archive folder in folder list - checked
Clean out items older than 6 months
Move old items to "path" - checked

Can anyone please help me!
P