Switching Users

  Hello, I'm having a problem switching users with XP Home Edition.

I do have the Welcome Screen and Fast User Switching enabled; however, after
I click Switch Users and return to the Welcome Screen, when someone else
tries to log on, he or she can input the password, but then it doesn't log
them on--it only returns to the Welcome Screen again.

I have been able to switch users for the past years, but the problem
suddenly started.  I have no clue what could have triggered it.

Thank you