After enabling the nvidia drivers for my optimus based laptop (Intel iGPU + nvdia discreet GPU), kwin crashed regularly. The main symptom was that application windows would not respond to mouse clicks, even though the mouse cursor still responded.

The fix was to create some symlinks in /usr/lib that pointed to a specific OpenGL library as apparently the nvidia OpenGL library was getting called by default (this should not be the case since optirun should be loading the nvidia libraries at run time).

This seems to have corrected the issue for now.

I built and installed the latest kernel (2.6.28 as of this writing) and attempted to install the proprietary nvidia driver with this kernel. The nvidia installer (version 177.82) did not detect the kernel headers that were in fact installed.

What I had to do was to extract the installation files from the nvidia installer (you do this with the -x flag). Then I had to apply a patch that I found here.

To apply this patch I cd'd into the nvidia installation directory created by running the installer with the -x flag. I downloaded the NVIDIA_kernel-177.82.diff.txt from the link posted above. The patch syntax was:
patch -p0 < /path/to/NVIDIA_kernel-177.82.diff.txt