Question : Problem: Locked PC username & password fields greyed out

This is an intermittant problem on Windows XP sp2 PC's in a workgroup invironment
When a PC is locked overnight, the username and password fields are greyed out in the morning.
Some users report the fields are white but they cannot type in username or password
The user has to restart the PC to logon.
If the user logs off at night there is no problem.
This problem started recently after doing Windows updates.
A search of expert exchange found a problem with early version of VNC. I uninstalled VNC but made no difference.
I have also tried resetting the local security policy as mentioned in another search.

Answer : Problem: Locked PC username & password fields greyed out

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