hidden system usage and mouse interrupts

Hi all,

cvsupped this morning (~8.00 UTC) and made world/kernel as usual (4BSD_SCHED).

systat shows me pulsing Sys-usage of 13/25%. Every 4 Seconds, the complete 
system "holds" for half a second. No mouse movement, keyboard delay, no 
sound.
Also pcm seems to be broken for me.

How can I find out what system process is eating my cpu cycles? top shows 
nothing.

Let me know if I can help with more info.

Thanks,

-Harry