At seemingly random intervals I am noticing that the number of threads being used by the 'kernel_task' is jumping from the normal ~63 threads to somewhere between 900 and 5000 threads. [See screenshot of Activity Monitor] This is on a 2.16Ghz 24" white iMac with a fresh 10.6 install. When the thread count spikes, the computer behaves very strangely. None of the menu-bar functionality works, I cannot bring up the force quit, logout/restart dialog boxes. The volume cannot be changed, and Apple-Tab does not bring up the app picker. Also, certain apps stop functioning. Any app that has audio or video playback (iTunes, browser with video/flash open, VLC, QuickTime) beachballs. QuickLook will only show "Loading..." for media files, but most still images and text/pdf documents will preview just fine. However, the dock functions normally, though sometimes clicking on an app will not bring its main window to the front. I cannot find any action that sets off the kernel_task, but once it starts, the thread count rapidly increases for about a minutes until it peaks, and then will slowly decrease until it gets back to normal range. If I let the computer sit for 30-45 minutes until the thread count is back to normal, suddenly all frozen tasks will resume at once as if all my actions had been buffered. I've opened Console to look at the logs but I don't know which file to look at, and none that I've viewed show anything that obviously indicates a problem. Any help would be appreciated, as I am restarting the machine 3 or 4 times a day!