"No Time" calendar events stop synchronizing with Outlook

When I enter a calendar event on my Treo 650 as "no time" it syncs with the Outlook 2003 calendar folder the first time (using VersaMail.) But future syncs cause some of the "no time" entries to either disappear from the handheld, or to change dates.

If I look at the Outlook Calendar folder and view the Recurrence Pattern column, the entries that get corrupted or lost on the handheld always show that field as blank. I found a workaround: I open the event in Outlook and click on Recurrence, then OK, then close the event. That populates the Recurrence Pattern field, which causes the missing or changed events to show up correctly again on the handheld after the next sync.

I never get any errors during my HotSyncs, and my "no time" events aren't showing up with an end time that's earlier than the start time (I've seen that in a few posts in the forum.) Not all of the events with the blank Recurrence Pattern field disappear every time, but the ones with that field filled in never disappear. And if I change anything on a "no time" event on the handheld like the spelling or alarm fields, it blanks out the Recurrence Pattern again in the Outlook Calendar folder and I have to fix it manually again.

I've tried hard resets, deleting and recreating user accounts and VersaMail accounts and renaming/deleting the Backup folders.