Suresh, thanks for the reply. Under logins, the login name is DomainName\UserName with Windows Authentication.

Under Credentials, the Identity is DomainName\UserName and the passwords have been entered (being an AD account, password doesn't change).

The weird thing here though is where can the name change anywhere else? To reiterate:

Entered: DomainName\UserName

Errmsg: DomainName\erName