to clear all keyframes
stand on your head and while drinking a picture of beer upside down thru a straw, 
then hold shift/alt/ctrl and click on the "-" sign next to the key in the animation palette.  This will delete all keyframes in the current scene at one time.

There is no undo (as far as I know) for this tho..so use it only if you mean to.

:)
BT