This might be a little oldskool for some people.
Do you remember that when the old original Mac (128K/512K/Plus) read a floppy disk that there was not enough time to deal with all the interrupts for the mouse movement? And that the mouse would jump around the screen?
The same thing just happened on my MacBook Pro after a couple of failed tries to wake the Mac up from sleep.
The hardware must have been confused or so because ‘top’ did not show any process sucking up all CPU time. I tried to sleep/wake the MacBook, turn the Airport off and on but nothing helped. After a reboot it is fine again.