Doesn't appear that OS 6 and the Mac DM like each other. Tried to sync on two separate Macs but no joy. Got referred to a DM knowledge base article which said delete certain service books. If I could figure out how, I would!

Any Mac users have the same issue?

No issues for me.
1. On the BB, Goto Options> Device> Advanced Device Management> Service Books. Delete: Desktop [CMIME] & [SYNC].
2. If you plan on sync'ing to more than one PC/Mac ... specify (allow sync to more than on computer.
3. ENSURE, ENSURE, ENSURE - that for each PIM component that you ENABLE Two-Way Sync'ing so not to purge your desktop information.

once completed go back to service books and select Menu> Undelete to get those service books for BES sync'ing.