When you press Ctrl+Alt+Del to sign in to your computer, you have to type the username each time. Windows does not remember the last username to sign in.
As of November 11, 2008, Windows computers joined to the TTU domain will not save the username of the last person to sign on to the computer. This security policy serves to further protect your eRaider credentials.
There is no known resolution at this time. The behavior is expected. You may type your username each time you need to sign in.