Software update just popped up this:

This update addresses a responsiveness issue on MacBook and MacBook Pro notebook computers. Some MacBook and MacBook Pro systems may occasionally experience a temporary suspension of keyboard input which can last a minute or longer. The Mac OS X 10.5.1 update is required before installing the MacBook, MacBook Pro Software Update 1.1.

It’s installing now. I guess we see if it works. Also it appears 10.5.2 is seeding to developers for a rumoured January update (presumably to support new hardware being announced at MacWorld or whatever it is).