Lost domain controller

I am a notice network admin. I recently inactivated a user profile and created a new one for our new secretary. Now, I cannot log on to the network on her computer, even though the computer is showing as connected to the network from another workstation. I believe I have authenticated the new user, but when we try to log her in, we get an error saying “Domain controller could not be found for the specified domain.” Any thoughts on what I may have done wrong?