Same problem here. My Macbook Pro keyboard and trackpad stopping responding randomly on a few different occasions very recently. Plugging in the USB Apple Mighty Mouse gave me control of the cursor again, but the keyboard/touchpad remained frozen.
Closing the lid to put it to sleep and reopening it seemed to fix the problem.
A side note: in "System Preferences" / "Keyboard and Mouse" / "Trackpad", the multitouch gesture demo video clips didn't display since day one, and accessing that "Trackpad" tab would make the text garbled, even after switching between tabs within "Keyboard and Mouse". I would have to exit "System Preferences" to reset it.
But when the keyboard/trackpad froze, and after I had plugged in a USB mouse to control the cursor, I noticed that the videos were working in System Preferences. Could this have anything to do with it?
I'm running OS X 10.5.5 on the early 2008 model of the Macbook Pro. This never happened before 10.5.5, though I can't say for sure whether it has anything to do with it.