"JACK server could not be started" when using Qjackctl

I have a problem when I try to connect my guitar to my computer, via line input. Audacity works well, and I can record what I play on my guitar (selecting from Preferences from where to record to default:line0). But the problem is in Qjackctl : at first when I click on start it shows this error:

after that when I click on Cancel it gives this error:

This is the log from the messages window:

10:30:37.368 Patchbay deactivated.
10:30:37.416 Statistics reset.
10:30:37.459 ALSA connection change.
10:30:37.497 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 request channel
jack server is not running or cannot be started
10:30:37.512 ALSA connection graph change.
10:30:44.060 D-BUS: JACK server could not be started. Sorry
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
Sat Dec  1 10:30:43 2012: Starting jack server...
Sat Dec  1 10:30:43 2012: JACK server starting in realtime mode with priority 10
Sat Dec  1 10:30:44 2012: control device hw:0
Sat Dec  1 10:30:44 2012: control device hw:0
Sat Dec  1 10:30:44 2012: [1m[31mERROR: Failed to acquire device name : Audio0 error : Method "RequestRelease" with signature "i" on interface "org.freedesktop.ReserveDevice1" doesn't exist
[0m
Sat Dec  1 10:30:44 2012: [1m[31mERROR: Audio device hw:0 cannot be acquired...[0m
Sat Dec  1 10:30:44 2012: [1m[31mERROR: Cannot initialize driver[0m
Sat Dec  1 10:30:44 2012: [1m[31mERROR: JackServer::Open failed with -1[0m
Sat Dec  1 10:30:44 2012: [1m[31mERROR: Failed to open server[0m
Sat Dec  1 10:30:45 2012: Saving settings to "/home/gevorg/.config/jack/conf.xml" ...
10:31:11.438 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 request channel
jack server is not running or cannot be started

Now I can't understand what my problem is.

None of these solved my problem. This did: http://dpod.kakelbont.ca/2015/08/16/fixing-qjackctl

1. In a terminal start qjackctl:

   qjackctl
   

2. Before you try to start it, click the Setup button in the GUI (right-hand side, middle).

   

3. On the setup GUI change Input Device and Output Device (middle, right-hand side) from (default) to hw:PCH (In the screenshot one has been changed and the other has not).

   

4. Restart qJackCtl. You should now be able to successfully use the Start button.

Try this from the command line:

pulseaudio --kill  
jack_control  start

Then when your done do this:

jack_control exit  
pulseaudio --start

And sometimes jack wont die, so then do

Get jackd's PID:

ps -aux | grep jackd  
kill -9 jacksPID

I made it and solved:

sudo killall -9 jackdbus