Whenever I select the iGPU, then after a reboot, I get my screen freezing (moveable cursor, but nothing clickable etc).
On Ubuntu 13.10, switching to the tty and back resolves this, but on 12.04 LTS a restart is needed.

This does not happen when the dGPU is active selection.

Is this a known bug, and anyone any idea any way to fix?

I've tried a host of things, from DPMS Off in my xorg.conf, to aticonfig ---services-off.

I'm using AMD Catalyst 13.12. There don't seem to be any obvious errors about the freeze in the logs.