I think I'm having the same problems:
HARDWARE/SOFTWARE:
* BlackBerry Pearl 8100
* Microsoft Outlook 2003 (no BES - using Web Client instead)
* BlackBerry Desktop Manager v 4.2.2.14 (Apr 26, 2007)
* Rogers Wireless (Canada) service
SYMPTOMS
* original sync w/ Outlook using Desktop Manager (USB) - no problem, all 2500+ calendar entries are common to both device and Outlook
* within 24 hours (whether or not another sync operation is performed), 2000-ish calendar entries are deleted automagically from the BlackBerry device
* always roughly the same number of deleted calendar entries (i.e. ~2000)
* does not affect Tasks, Address Book (Contacts) or Notes which are sync'd the same way
* re-sync'ing between Outlook and device causes Desktop Manager to try and DELETE all 2000-ish messages from OUTLOOK; but, performing a "Resync" correctly adds them back to the BlackBerry device
TROUBLESHOOTING SO FAR (NOTHING HAS WORKED):
* wiped handheld
* reinstalled Desktop Manager and device software
* disabled the "Wireless Reconcile" feature
* swapped out device hardware (for refurbished model)
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Aaarrrrgghhhhh!!! This is driving me crazy! If anyone has a similar issue and has found a resolution, please lemme know.
Cheers,
Jeremy