CPU usage high while in kernel call

While a kernel is running (any kernel), my CPU (not GPU!) usage sits at 50%.

Is anyone else experiencing high CPU usage while a kernel program is running?

WinXP Pro 2002 SP2, Dell Precision 390

[edit: more parameters]
GeForce 8800 GTS

yes i am having the same problem right now… its killnig my gaming.

though i am runnig a 7800 gs oc

That’s probably due to a call to cudaThreadSynchronize(). cudaThreadSynchronize is basically a function that does some busy waiting until a kernel is finished.
It is said that one of the next CUDA releases will provide means of circumventing this.