I resolved this issue with RIM support by (1) clearing my device Calendar (2)Importing my PIM (Outlook) tasks (3)Turning back on sync.
I still have the wireless sync turned off. But at least now I can enter calendar items in device and PIM - and manually sync.
I am not sure I would recommend BB to heavy MS Outlook users. I cannot believe the sync issues I solved with my Palm IIIx and Hotsync to Outlook 1998 via serial cable are coming back to haunt me in 2006 in a Blackberry - same old bugs a decade later!!!
I would probably go with the Windows Mobile device now the Exchange 2003 can push email.
It's a good bet I'll be there < 2yrs myself!