[sevendx7]

this is probably way too simple to resolve your issue, but maybe not:
I received the same error on my 800 when i tried to setup a new exhcange account through the "add email account option". However, whenever I went under the email account settings and then under the "outlook email" tab and entered my exchange info it worked perfectly. I don't know if this helps or not. i also had this exact same issue/resolution on my mogul