This might be a need to get the user name right. Have you tried:
- username
machinename\username
domainname\username
Did all three fail?
Try connecting via telnet (Start > Run > telnet machineID); your Windows authentication should be OK here.
Select the UV account.
Shell out to the operating system with the command DOS.
Look for a file called dsinstall.txt. This should show you the identity of the intalling and administrative user. You could try connecting from your client using either of these.