Hi Anne et al.
It's odds-on that acceleration method is the key. Intel and ATi
rapidly developing their drivers to meet the more stringent requirements of
recent distros. Kde4 desktops in particular uses parts of the driver not
stressed in older versions. On this laptop I have an ATi display. The
desktop works best with AccelMode set to EXA, but kuickshow has corrupted
display in EXA and looks fine with XAA. It really does seem to be something
where you just have to experiment.
You might find http://userbase.kde.org/GPU-Performance
since I've switched AccelMode to XAA on my latop with the old i830
chipset, I didn't see any graphics corruption. I don't use desktop
effects on this machine anyway, so I'm not missing out on any bling