My 2 cents:

Stick with this version of kernel: 2.6.9-11.EL if you want to run a stable box. It was a nightmare for my box to run any of the latest kernels that rhn releases. The problem is virtual memory management, the box swaps like crazy even though has plenty of free memory sitting around. The load on the box is unbelievably high because of kswap running at all times.

If you updated the kernel of your server and you notice a load spike, your kernel might be the problem. I tried tweaking the /proc/sys/vm settings but it didn't fix the load problem.

I hope the kernel developers know what they are doing....

Albo