What is causing the high system CPU load under Mountain Lion? I recently began to see some odd behavior on my MacBook Pro on Mountain Lion. I noticed the fans coming up and applications behaving sluggish. I checked the 
ActivityMonitor (see below) and the results kept me puzzled: Although I list all processes, only very few show up that cause medium CPU usage, still the system CPU is at close to 70%.

I've wondered about this behavior quite a while ago already and then - just as now - the problem just went away after about 10-15 minutes of lagging and fanning.

What can cause these symptoms? Why isn't the "thing" causing the CPU load showing up in the process list? How can I diagnose the issue in more detail?

UPDATE: I seem to could have hunted it down to Skype causing the trouble. I've notice it running on 100% CPU and quit it. Now it seems to hang in some kind of error state according to ps. Unfortunately I cannot kill it :(.

$ ps -xo pid,ppid,stat,command | grep Skype
85267   185 ?E   (Skype)
79202   339 R+   grep Skype
$ kill -9 85267
$ ps -xo pid,ppid,stat,command | grep Skype
85267   185 ?E   (Skype)
79220   339 R+   grep Skype
Try opening a terminal and type 

  ps -AaC


The CPU time there is cumulated time spent executing, but maybe a process will show with an all time cpu use that sticks out somehow.

There also seems to be an answer to a similar question here which suggests Intel Turbo Boost may be the culprit.