[LAU] qjackctl fails to exit gracefully on UbuntuStudio 10.4

I recently did a fresh UbuntuStudio 10.4 amd64 install. I found that I could only start qjackctl once without rebooting. When I attempted to close jackd with the Quit button on qjackctl, the next attempt to run it results in the following message: JACK compiled with System V SHM support. loading driver .. Enhanced3DNow! detected SSE2 detected apparent rate = 48000 creating alsa driver ... hw:0|hw:0|256|2|48000|0|0|nomon|swmeter|-|32bit control device hw:0 23:08:49.544 JACK was stopped successfully. 23:08:49.544 Post-shutdown script... 23:08:49.545 killall jackd 23:08:49.549 JACK has crashed. jackd: no process found 23:08:49.993 Post-shutdown script terminated with exit status=256. 23:08:50.025 Could not connect to JACK server as client. - Overall operation failed. - Unable to connect to server. Please check the messages window for more info. Neither "sudo kill -9 <PIDs of jackd, qjackctl and qjackctl.bin>" nor "sudo pkill -9 qjackctl" nor closing the terminal in which qjackctl was executed eliminates this problem. Since this was a clean install with very little added beyond ambdec, tetraproc and mhwaveedit, I don't have any explanation for this problem except bad karma between the current UbuntuStudio and qjackctl. On one occasion when starting the reboot, I got an error message asking if I wanted to wait for process Unknown to complete. The good side to this is that UbuntuStudio 10.4 boots up quickly. Does anyone have any ideas? Thanks, John