nvidia-smi fails with cuda 4.0

I installed CUDA 4.0 and after a while I got fallowing error:

gkokosinski@cuda2:~/kmeans$ nvidia-smi -q

NVIDIA: could not open the device file /dev/nvidia2 (Input/output error).

Nvidia-smi has failed because your system has at least one NVIDIA GPU that is insufficiently

powered. This may be because not all required external power cables are attached, or the attached

cables are not seated properly.

What can I do?

I found http://forums.nvidia.com/index.php?showtopic=196791 , but I didn’t help ;/

I installed 4.0rc2 and everything start working once more. It is weird that main release 4.0 is not working, but rc2 does.