I use Command-Tab a lot on my powerbook G4 17", and once every week or so, the act of doing a Command-Tab takes me into the appswitcher overlay, but I can't get back out of it. Keyboard does nothing, and the mouse moves around, but clicking has no effect. The machine is still responsive, and I can ssh in, but killing Finder just leaves a zombie. My only recourse is to reboot.

Anyone have a clue, or tips on how to troubleshoot/fix something like this? Are there any magic processes I can kill/restart that may fix this while still leaving me logged into my desktop?