Leopard kernel using 60% cpu?

Ok I just installed leopard over tiger and suddenly my kernel_task is using 60% cpu 162 real memory 1.15 GB virtual. it can't be bad RAM because it was working perfectly yesterday.

What can I do about this? if i load up streaming videos and watch them for more than 10 minutes it completely overloads the box and I have to force restart.

And restarting takes about 5 minutes for some reason.

I've already verified and repaired permissions on the disk (didn't need it) both from the normal OS and the startup disc.

Running on a macbook pro 2.2 ghz intel corre 2 duo with 2GB 667 Mhz RAM

thanks in advance!