One particular user in our system is unable to connect to Exchange ActiveSync via her iPhone. When I try to connect using my own credentials on her iPhone it works (everything begins syncing), but when I input her credentials, the Settings app verifies the credentials are correct but nothing syncs. For example, if I open Mail, no items are shown. When I attempt to force a sync, it says "Cannot connect to server."

In Exchange 2010 Management Console the user is no different than the others. Exchange ActiveSync is set as "Enable" in Mailbox Features.

EDIT: Alternatively, if there is some easy way to create a new useraccount/mailbox and copy all of the contents of the old one over, I bet it would work, and that would be fine as well. She is a Mac user so we do not have to worry about her Active Directory account.