KDE 4.5 OpgnGL compositing with fglrx

[ssteinberg]

OpenGL vendor string: ATI Technologies Inc.
OpenGL renderer string: ATI Radeon HD 3850
OpenGL version string: 3.3.10057 Compatibility Profile Context
OpenGL shading language version string: 3.30

Using ATi drivers 10.7. OpenGL composition worked perfectly with xf86-video-ati, however I can't enable it with fglrx, even when checking the "disable functionality checks" checkbox.
~/.xsession-erros gives:
kwin(3238) KWin::Workspace::setupCompositing: KWin has detected that your OpenGL library is unsafe to use, falling back to XRender.

OpenGL applications work flawlessly.

KDE 4.5, kernel 2.6.36, Xorg 1.82.

Any clues?

[mimi.vx]