KDE startup and shutdown problems

Kubuntu 12.04, KDE 4.8.5

Hello!

I'm having one or two difficulties with the KDE startup and shutdown procedure at the moment.

My issue began on Monday. I logged into KDE as normal, but instead of getting the startup screen, I instead got a black screen with two or three lines, the last of which was:

Stopping System V runlevel compatibility

and I was then returned to the login screen. I logged in again and it happened again. And again. And so on.

After digging around the Linux messaging forums, I eventually found the solution that enabled me to login successfully:

sudo service kdm stop
startx -- :0 (or startx)

All my settings, programs and internet browser tabs have been preserved. However, I have discovered that I have no authorization to access any removable drives and there is no audio on any clips I play, on- or offline.

When I clicked to leave the session, I discovered that the default leave options do not display the icons for 'Turn off computer' or for 'Restart computer'. I was dismayed by that, as it suggests I've logged into an additional session with a session still running, which appears to be confirmed by

clive@clivubu:~$ ck-list-sessions
Session2:
        unix-user = '1000'
        realname = 'Clive Nicholas'
        seat = 'Seat1'
        session-type = ''
        active = FALSE
        x11-display = ''
        x11-display-device = ''
        display-device = '/dev/tty1'
        remote-host-name = ''
        is-local = TRUE
        on-since = '2013-01-23T17:00:23.096660Z'
        login-session-id = ''
        idle-since-hint = '2013-01-23T17:01:48.542131Z'
Session3:
        unix-user = '1000'
        realname = 'Clive Nicholas'
        seat = 'Seat2'
        session-type = ''
        active = FALSE
        x11-display = ':0'
        x11-display-device = '/dev/tty8'
        display-device = '/dev/tty1'
        remote-host-name = ''
        is-local = FALSE
        on-since = '2013-01-23T17:01:21.410602Z'
        login-session-id = ''

Checking the Session Management settings show they are at their default settings. Selecting 'Start with an empty session' and restarting changes nothing.

Selecting 'Log out' on leaving, then typing logout at the terminal prompt and then switching my machine off and on to login again produces the same login issues as in the beginning, only this time it produces more statements at the black screen, which I have been able to capture:

Stopping log initial device creation
Starting enable remaining boot-time encrypted block devices
Starting configure network device security
Starting configure virtual network devices
Stopping configure virtual network devices
Stopping enable remaining boot-time encrypted block devices
Stopping System V runlevel compatibility

after which I am then returned to the login screen.

I have never encountered this before and would obviously like to resolve whatever problem is causing this issue. Does anybody have any idea as to what is going on?

Thanks in anticipation of your help.