Windows

Is this an NT4 box? Seems I remember a problem like this and had to unload Norton Antivirus Corporate services then reload it to fix it. Not uninstall, just unload and reload. In fact unload, then test it, then reload.

I have not heard of that before, but I would try going another route to the user accounts and see if that works. Go to administrative tools -- users and groups -- users in NT4
or
Control Panel -- administrative tools -- computer management -- users and groups -- users from Win2k, WinXP

there are multiple paths you can take to get to the users section or admin the users in XP. If Control Panel->User Accounts is not working for you, try one of these two options.
1)go to start->right click on "my computer" and select "Manage".
Now on the Left side pane, you would see "Local Users And Groups" under the system tools section.
click that, and on the right side you would see two folders Users and Groups. double click on Users, and it will display all the users on your machine.

2)If that does not work for you either, then go to start->run->type in MMC.
When the MMC windows opens up. go to menu-->
File->Add/Remove Snapin.. or just press "ctrl+M"
When the Add/Remove snap in windows comes up, click on the add button.
From the list, scroll down and select the "Local Users and Groups", click add, it will prompt you, just click finish on the prompt.
Now click Close
Now click OK
Expland the "Local Users and Groups"
Click on Users, and you will see all the users on your machine in the right hand side pane.

Hope it helps