Whenever I minimize a window to the dock on my sister's Mac Mini (currently running Panther), the screen will freeze for a split-second, fade out to the default solid-blue background (as though it were logging out) and then fade back in. This also happens repeatedly once the screensaver is active for more than five seconds--you have to move the mouse for almost a minute before it finally calms down. At first I thought I'd broken something when I installed TinkerTool, so I restored all the default settings and the problem went away for a while. Then my brother logged into his account and he started experiencing the same problem. We're all recent Mac switchers, so any help is appreciated.