Outlook mobile is much like Outlook desktop in that it passes traffic through a middle-man service. That middle-man service does a fair amount of caching as well, so the speed at which you're moving through this testing could definitely be a contributing factor. What if you rename the account to a totally different username that has never been used in Outlook mobile? Does it sync there? You will also want to give it some time to finish it's initial sync since it will need to sync everything up to Microsoft then down to your client.
Kyle Kerst
IT Coordinator
SmarterTools Inc.
www.smartertools.com