I've noticed this with other versions of KDE. I'm using a generic Intel Graphics Controller:
Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03)
Sometimes when I log in, KDE will kill the compositor (claiming the laptop's hardware is overtaxed). As soon as I enable it, one or both CPUs crank up to a 100% and KDE essentially locks up until the compositor is automatically disabled. (It will disable compositing even if I uncheck the option!)
If I logout and back in, KDE works beautifully with full compositing. The problem disappears.
Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03)
Sometimes when I log in, KDE will kill the compositor (claiming the laptop's hardware is overtaxed). As soon as I enable it, one or both CPUs crank up to a 100% and KDE essentially locks up until the compositor is automatically disabled. (It will disable compositing even if I uncheck the option!)
If I logout and back in, KDE works beautifully with full compositing. The problem disappears.