Account Error with 2008 R2 Box

I have just created a new 2008 R2 box which is a domain manager and moreover, it has the terminal services function installed.I have three accounts; the first one is the default administrator account, the second account is known as admin1 by domain admin rights and the third one is user1 account. All three accounts worked with no problems. However, now it looks like my user1 account has not been working; it may be locked out.  And I am getting the following error message:

You cannot log on because the logon method you are using is not allowed on this computer. Please see you network administrator for more information.

The account is not halted; however, I have no clue why this is occurring while it used to work all right. Please help. Thanks in advance.