I'm having an issue where, relatively repeatably (though not every time, so it's hard to test) Tiger will freeze when switching users with Fast User Switching (sorry about the lame pun in the title--couldn't resist). Basically, about 5 or 10 seconds after the user switch completes, you suddenly can't click on anything on the screen with the mouse (though the pointer will still move), then a little later it will freeze completely. It's not likely application-related, as it happens even with almost nothing running. So far I haven't found anything interesting at all in the logs--no panic is logged, and there's really nothing at all logged as going on at the time of the freeze. These seem to (almost?) always occur right after the computer has been woken up, but I *think* that's just because the way my computer gets used my wife or I usually wake it up after the other has put it to sleep then switch to our own account. It happens going both ways, so I don't think it's specific to one user. Stranger still, it started happening on at least a daily basis (sometimes more) last week after over 20 days of uneventful uptime with 10.4.2, and I hadn't changed *anything* when it started. I even removed unnecessary USB devices after it started acting up, but no love. I've tried everything I can think of: PRAM and NVRAM reset, permissions repair, all the latest OS updates, disk check, run the hardware test CD (no problems), and even the "deep cleaning" option in Tiger Cache Cleaner (as well as all the other maintenance stuff). One suspect I had was the ATI Displays Control software, which was nice but occasionally crashed (with no apparent ill effect other than the dialogue) after switching users. I disabled that but it hasn't helped. Anybody ever seen such a situation? This is a pretty much clean Tiger install with only a few add-ons, so I'm kind of baffled and really don't want to reinstall. I just did the latest security patch, so who knows, maybe that'll help.