I discovered a weird interaction between f.lux and fullscreen gaming. They seemed to fight about which gamma etc to use.

It was nothing you could see, and other than a jerky in-game mouse you did not notice it. And after an hour of playing, dying cmd+tabbing out to Safari to surf while waiting for respawn, WindowServer core dumped, logging out all users in an instant.

This is fixed in 10.10.3. The jerky mouse pointer problem still remains. I don't use f.lux anymore.