Apart from Kwin disabling compositing, absolutely no problem with maverick KDE using the as-delivered open source drivers here. One solution is to use compiz for KDE rather than Kwin.
Originally Posted by tball
Apparently the Kwin developer does not do extensive hardware checking, and the driver he was using for his R700 ATI card on his distribution didn't work, so he has disabled Kwin compositing for everyone using the open source R600c driver.
Another work-around for Kubuntu maverick:
Workaround - not a fix
Using the force - don't worry, be happy settings
Editing the ~/kde/share/config/kwinrc.
LIBGL_ALWAYS_INDIRECT=1 kwin --replace
The desktop effects are working...