i think i'm having the same problem. Had encountered the error 'Unable to logon to Pocket Outlook Database' in Pocket Informant a couple of weeks ago. While everything else works fine, I couldn't see my PIM data and can't even start Pocket Outlook. Had to do a hard reset.
Now the problem has surfaced again, and activesync failed.
I will try remove and re-install Activesync as bilyth has suggested and see how it goes..