I know with the 1ghz I have you run an external display with the PB closed. I'm assuming to desktop pattern is all your seeing, no top menu bar?
If that right then try turning it on with an external display and a mouse and/or keyboard, then put it to sleep i.e. close it.
Then wake it up by pressing a key or mouse button with the PB still closed. The external monitor should come on as the only diplay. Kinda like a fake tower mode. I don't know what PB this works on but it worth a shot
It happens to me every now an then when I'm moving stuff on my desk PB asleep and the LCD I have hooked up comes on.
Peace
MM-o4