I got the same error the other day as well. I cannot remember the exact process I did to fix the problem but I think I had the create another Outlook profile with a totally different name e.g instead of 'Zimbra' I called it 'username-zimbra'.
I also tried the other things you did (delete zdb etc) with no luck. Give the profile name a go and maybe even remove the ZCO connector totally and install it again. I cannot get to the PC I did this on right now but i know it was a simple fix.
Paul |