Weird Win 2000 boot up after SP4, any ideas?

The computer will start up fine if you log on as Administrator. If you log off Administrator and then log in as another user, that works ok also. But if you try to log in as another user first thing, it freezes. It happens right after the message goes by about checking your settings. All the icons have appeared on the desktop, and the hourglass just stays there.

When this happens, I've tried to get into the Task Manager to see what's going on. But I can't get in. When I try, the icons all disappear and the Task Manager never opens.

This isn't a computer that gets a lot of use, and catching up on Windows Update is the only thing that's been done to it recently. So I'm assuming its a problem coming from that.

Any ideas, other than just leaving it on Administrator all the time? I don't necessarily want other people to have access to all those features.