Just had another crash. Same scenario: kernel compile, browsing, e-mail etc.
BTW, I have two pointers: Synaptics touchpad and a PS/2 mouse. Is it possible for X to go haywire if it can't talk to its CorePointer (touchpad)? Maybe under heavy load things become "slow" on that front and X interprets that as no pointer?
X does get confused when the mouse is plugged in while X is starting and then it won't run at all. It claims that CorePointer isn't there. Weird...