Outlook calendar items no longer sync with PDA

I have a Dell Axim X50 with Pocket PC 2003 and on my computer I have Outlook
2003 with Windows XP. My Activesync worked well until recently when many of
my calendar items which continue to appear in Outlook on my computer do not
get transferred (or disappear) from my pocket PC. I had downloaded AS 4.2 and
thought that might be the problem so I removed it and just have 4.1. However,
the problem persists. I have tried both choices - sync all appointments and
sync the last 52 weeks past and future - in Options in the AS on the computer
and get the same poor result. I welcome new ideas!
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ASO