Okay, I sorted out what the problem was for me and got it resolved today. This may or may not be the same situation as for you gfator24, but I'll post anyway.

As I had said, my calendar originally synched just fine but then the problem started. After some pondering I figured that it might have something to do with all the futzing around I did with e-mail addresses trying to get my ISP's (Comcast) BIS-based e-mail to hit the BB device in real time. In the process of doing that I had created a VZW blackberry e-mail address at BIS and forwarded my Comcast mail to the BB on the server side. So far so good. But after modifying the VZW BB e-mail account to look like my Comcast account, I deleted the Comcast account from the BIS.

All of this rambling to say that it seems that my default calendar on the BB got changed from the Comcast account that was synching successfully with Outlook to the new VZW BB account. Which has no calendar.

Anyway, after adding the Comcast account back to BIS, I found what seems to be the problematic item under Options - Advanced Options - Default Services. The entry under "Calendar (CICAL)" was the VZW BB account, not my Comcast account. I had since added the Comcast account back to BIS, and was able to "Change Option" to make the default item the correct account. Went back to desktop manager and Voila! The account was found.

The first time I synched I had dup records of everything, but was able to clear everything out from the calendars on the BB using the backup utilities in DM and then get a clean synch.

Again, don't know if this will help you at all, but it turned out to correct my problem. Best of luck.