I recently reinstalled Windows XP Home SP2, with SP3 slipstreamed. I then installed a bunch of patches. I never used Fast User Switching before, but I have been since reinstalling Windows. Sometimes when I try to switch users, I can't type a password on the welcome / logon screen. Seems random. My 2 users are displayed, and I can click on both names, but the mouse cursor remains a hand, no cursor appears in the password box, and typing has no effect. I have to reboot the computer to be able to do anything. My searching has turned up a lot of complaints about the same or similar problems and I've seen a few different suggestions about the cause. In some of those cases it's unclear whether the problem being described is only affecting the logon screen when the computer is first booted, or when switching users as in my case. These are some of the possible causes that have come to my attention: * Installation of Windows patch KB923191 (or other -- see http://support.microsoft.com/kb/917556 ) -- KB923191 is included in Service Pack 3. The support page suggests "Press CTRL+ALT+DEL two times while the Welcome screen is displayed" as a workaround. I didn't know about that the last time I ran into the problem. Once I found out, I started the process of switching users to get to the logon screen to try it. So far the times that I've tried that, the problem hasn't occurred when I get to the logon screen and pressing CTRL+ALT+DEL twice doesn't do anything. I'm hopeful, but doubtful, that when the problem occurs, it will work. * "keys that lead to removed/non-existing or disabled services" in the registry at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify (see post by Guillaume at http://help.wugnet.com/windows/Login-unable-type-password-screen-PCsftopic-531822-days0-orderasc-24.html#2220461 ) -- Guillaume's post mentions "In my case AtiExtEvent key caused all the trouble, not any of the file versions in the hotfixes." I have the ATI Catalyst drivers / Control Center installed, but not .NET which Catalyst Control Center requires (therefore it won't start), and I have the registry key Guillaume refers to. * Some kind of lockout imposed by Windows -- I checked Event Viewer and there are "Failure Audit" entries that may correspond to the most recent incidence of this problem. Source: Security Category: Account Logon Event ID: 680 Logon attempt by: MICROSOFT_AUTHENTICATION_PACKAGE_V1_0 Error Code: 0xC000006A Searching that error code value was what led me to mentions of account lockout. However, a post by Adrian Florin Moisei at http://www.eventid.net/display.asp?eventid=680&eventno=2267&source=Security&phase=1 seems to suggest this event would routinely be logged each time the welcome screen is displayed. What gives? What do I do?