Mystery as to why we're not able to connect from...

Question

Scenario:
Windows 7 laptop in a Windows Domain environment is attempting a straight RDP session to a non-Domain Windows server 2008 R2. Laptop (System A) gets rejected every time using correct local Administrator account and verified correct password on non-Domain
Windows 2008 R2 server (System B)
Any ideas or scenarios that may cause this kind of behavior (other than bad password which has been totally eliminated as a variable)???
Facts:
I can remotely log in to (System B) using LogMeIn and the Administrator account and password referenced above. I can also log in to (System B) from another non-Domain (System C) server using same credentials as above, without any problems. (System B) has
NO GPO's applied (verified by GPRESULTS) but I cannot speak to (System A). Owner of (System A won't help out anymore so I need some possible ideas or things that
may cause this kind of behavior)
User who has problem claims to also be able to log in to (System B) from a non-Domain Linux and Mac OSX box.
Error message seen in Windows Event Log:
An account failed to log on.
Subject:
Security ID:
NULL SID
Account Name:
Account Domain:
Logon ID:
0x0
Logon Type: 3
Account For Which Logon Failed:
Security ID:
NULL SID
Account Name:
administrator
Account Domain:
SKYDIVE
Failure Information:
Failure Reason:
Unknown user name or bad password.
Status:
0xc000006d
Sub Status:
0xc000006a
Process Information:
Caller Process ID:
0x0
Caller Process Name:
Network Information:
Workstation Name:
MA-LT-TP
Source Network Address:
Source Port:
Detailed Authentication Information:
Logon Process:
NtLmSsp 
Authentication Package:
NTLM
Transited Services:
Package Name (NTLM only):
Key Length:
0

Answer 1

Hi,
As a workaround please add the following line to the .rdp file (using Notepad) that the user double-clicks to connect to the server:
enablecredsspsupport:i:0
If they do not have a .rdp file for this server they can create one easily by entering the name, configuring settings, etc., in the Remote Desktop Client and then clicking the Save As button.
After making the above change please have them verify that they are able to connect.  If the change was performed correctly they should get the server logon screen instead of the frontside authentication prompt.
Thanks.
-TP