unable to start Jackd

unable to start Jackd

I am trying to start Jackd. I am a newbie.
Below is the message which I get when attempting to connect jackd.
Could you experts please check and advise what I must be doing wrong?
Thanks in advance.
23:22:22.450 Patchbay deactivated.
23:22:22.465 Statistics reset.
23:22:22.837 ALSA connection change.
23:22:23.502 D-BUS: Service is available (org.jackaudio.service aka jackdbus).
Cannot connect to server socket err = No such file or directory
Cannot connect to server socket
jack server is not running or cannot be started
Registered event listener change listener:  true
23:22:23.520 ALSA connection graph change.
23:22:27.794 D-BUS: JACK server could not be started. Sorry
Cannot connect to server socket err = No such file or directory
Cannot connect to server socket
jack server is not running or cannot be started
QSpiAccessible::accessibleEvent not handled:  "2"  obj:  QMessageBox(0xbf906580) ""
FIXME: handle dialog start.
Sun May 19 23:22:27 2013: Starting jack server...
Sun May 19 23:22:27 2013: JACK server starting in non-realtime mode
Sun May 19 23:22:27 2013: [1m[31mERROR: Cannot lock down 82241434 byte memory area (Cannot allocate memory)[0m
Sun May 19 23:22:27 2013: control device hw:0
Sun May 19 23:22:27 2013: control device hw:0
Sun May 19 23:22:27 2013: Acquired audio card Audio0
Sun May 19 23:22:27 2013: creating alsa driver ... hw:0|hw:0|1024|3|44100|0|0|nomon|swmeter|-|32bit
Sun May 19 23:22:27 2013: control device hw:0
Sun May 19 23:22:27 2013: [1m[31mERROR:
ATTENTION: The playback device "hw:0" is already in use. Please stop the application using it and run JACK again[0m
Sun May 19 23:22:27 2013: [1m[31mERROR: Cannot initialize driver[0m
Sun May 19 23:22:27 2013: [1m[31mERROR: JackServer::Open() failed with -1[0m
Sun May 19 23:22:27 2013: [1m[31mERROR: Failed to open server[0m
Sun May 19 23:22:29 2013: Saving settings to "/home/alcuino/.config/jack/conf.xml" ...
FIXME: handle dialog end.
23:22:43.101 Could not connect to JACK server as client. - Overall operation failed. - Unable to connect to server. Please check the messages window for more info.
Cannot connect to server socket err = No such file or directory
Cannot connect to server socket
jack server is not running or cannot be started
QSpiAccessible::accessibleEvent not handled:  "2"  obj:  QMessageBox(0xbf906e10) ""
FIXME: handle dialog start.
FIXME: handle dialog end.
QSpiAccessible::accessibleEvent not handled:  "6"  obj:  QMenu(0x85071b8) ""