A few things to try ...
... are included on that Blackberry support page.
Verify that the Mapi32.dll and CDO.dll files match version-wise. One resides in the win\system32 and the other in your exchsrvr\bin directory. There are some microsoft kb's on that if they dont match.
RIM would have you remove certain service books and then to a "Resend Service books". That is in the Options/Advanced Options on the device. They usually remove the Desktop SYNC, CMIME, CICAL. One thing they told me was to change the amount of days to "KEEP APPT" in the calendar from the default 60 days to 15.
Also, I know this sounds stupid, but I was having the same issue where all 8 devices would stick around the 56% mark on activation. I looked in my EventVwr and had multiple BiPPeClient connection errors. I even got on the phone with RIM and you know what fixed it .... you got it, a @#@$@%@^ reboot!
The tech I talked to, who was great, said she had seen this happen frequently in the past few weeks with version 4.1.4.x. I don't know how easy it would be to reboot but its worth a try. Would have saved me 4 hours!