Yesterday I had a little problem with the iBook, which was saved by some age-old knowledge from before the OS X release. Almost.
When I use an external USB mouse, I disable the internal trackpad. Now I wanted to take the computer into a different room in order to watch some TV (on the EyeTV), so unplugged all the USB stuff, plugged the EyeTV in....and the trackpad was still disabled. Now, a lesser person would have gone back into the original room, plugged the USB mouse in, and used it (or taken it with them). An equally lesser, but richer, person would own a Bluetooth mouse. But not I! I remembered a trick from the NeXT days, and returned my computer to trackpad-workingness in but a jiffy. Three jiffies.
The first thing to do is to log out - "as any fule kno" this is done from the keyboard by Command-Option-Shift-Q. At the loginwindow there still wasn't any trackpad activity, so I thought restarting the WindowServer might fix that. This is done by entering ">exit" as the username in loginwindow. Sadly, no joy. My next thought was to drop to a text console, unload the trackpad's driver kext, reload it and see what difference that made. Doing so requires entering ">console" as the username. However I decided not to pursue this as >console has been sadly broken throughout 10.4, and on some systems was broken in 10.3 too. It's annoying as occasional glitches where the graphical environment is FUBARed could probably be fixed in console mode. But this left one course of action. Enter ">restart" in the loginwindow and wait...
I should probably point out that I waited for the reboot longer than it would have taken to retrieve the mouse. But at least I wasn't defeated.