I was running a simulation and everything went south (my fault, stupid coding error). So I quit the kernel. Everything was running very slowly, as if it were doing some kind of large calculation. Eventually I quit Mathematica. Everything continued to run slowly. So I opened up the terminal to see what processes are running (I'm on Mac OS 10.6.8, Mathematica 9.01) and observed that there was a "Mathkernel" process, using about half (and sometimes more - 57.2% in the sceenshot) of my CPU. I tried the "Kill" command, and even "sudo Kill" but it didn't even blink. I tried logging out and back in, but it was still there. Finally, I restarted my computer, and it was gone. My question: is there a more elegant way of recovering from such a runaway process?