Hi,
Its not an ambiguous error the login is failing, triple checking or not, something isn't right in the connection string or the user account doesn't have permissions as you think. I recommend using a sql user not an AD user. If you use a windows user you may need to use the same user for the aspnet user that the web runs as and you may need your connection string formated differently. The format on the included connection string is for a sql user account.
I also recommend using the latest version of mojoPortal, currently 2.2.8.2-b
Hope it helps,
Joe