Description of problem:
NVIDIA 1.0-5336 drivers compile OK with kernel-smp-2.6.3-2.1.238,
but sytem hangs completely with blank screen after startx.
Reverting to kernel-smp-2.6.3-1.118 clears problem.
No errors found in /var/log/XFree86.0.log or in $HOME/.xssesion-errors

Version-Release number of selected component (if applicable):
kernel-smp-2.6.3-2.1.238.i686.rpm
NVIDIA-Linux-x86-1.0-5336-pkg1.run

How reproducible:
100%

Steps to Reproduce:
1. as root, build NVIDIA drivers
2. as regular user, startx
3.
  
Actual results:
total system hang requiring power-cycle to clear

Expected results:
working system 

Additional info:
Yes, I know NVIDIA taints the kernel.