Exposé problems...

Every once in a while Exposé decides to erase the key bindings to it... I either have tio just go set them again, or I can restart the computer and they will auto restore. I have no idea, when, why, or how it happens I just know every once in a while i try to use it and it doesn't work and I go check the settings and sure enough they are gone.

any idea why this happens, and how to fix it?

try resetting the pram.
restart while holding command+option+p+r
when you hear the second boot sound, let the buttons go.