You can try shutting down classic by launching the process viewer in X, and then force-quitting Classic by double-clicking on its name in the list of running processes (if you don't see it, try changing to "View all processes" from the drop-down menu in the upper right corner of the process viewer window). You're given a choice of either quitting or force-quitting. One of the two should force Classic to shut down.
You might also want to quit or force-quit the process called "TruBlueEnviromen." I'm not sure what this process does, but I've only seen it running when Classic is also running.