Kit AMD 4 core cpu + onboard Radeon HD 4200 GPU, twin head.
Kernels:
Fedora 18 - 3.7
LinuxMint - 3.5
Desktop - KDE 4.9

Symptom: Screen will not update (ie: menu drop downs, gif animations (Firefox), content assist boxes (Eclipse) will not appear (or animate) unless the mouse is kept moving. Text cursor (caret) flashing likewise stops unless the mouse is kept moving.

Also:
Installation of both distros was problematic, I kept having to move the mouse or hit a key otherwise the install process would stall.
Older kernels (3.5 in Fedora 11) work perfectly on the same hardware.

What I've tried:
Installing proprietary ATI driver (fglrx).
Setting pci=noacpi kernel parameter (and others).
Trying sun java instead of iced-tea (for Eclipse).
Disabling Desktop effects.

All to no avail.

This appears to be a generic kernel problem - any suggestions would be greatly appreciated. I haven't included any logs as they all look pretty reasonable - no glaring errors - the system is otherwise stable.

UPDATE: SOLVED (Sort of.) The APIC was not getting set up properly, altered /etc/default/grub to include nolapic_timer. This made animations, content assist etc. work perfectly. Firefox works much better altogether.