PMP Build 11000 - AD Authentication in null domain

PMP Build 11000 - AD Authentication in null domain

Hi Guys

Has anyone hit this problem with PMP when a user is trying to log in with AD Authentication?
We're currently hitting it with 1 user. All others are able to login fine so far anyway.

When they try log in they just get the Username/Password incorrect error and the user audit trail as Username:Not Applicable and the Reason: AD Authentication in null domain.

We've confirmed the username/password is correct and the account isn't locked. We've attempted to reimport the user account which confirms it already exists.

I can see some mentions of this issue in the ServiceDesk PLus community but don't know how much it would relate to PMP. Any ideas on this?

Cheers!
Eoin