killall -STOP TruBlueEnvironment
This will pause Classic so that it doesn't eat your CPU. When you're ready to use Classic again, unpause it by doing this:
sudo killall -CONT TruBlueEnvironment
You have to use sudo because attempting to restart the process as a regular user will result in an "Operation not permitted" error. I haven't yet been able to figure out why this is.
[robg adds: You can use this technique to pause any process, as explained in this hint.]

