In Tasma>System>User Manager Add a new user with a mark at Groups:
(one of the above is necessary to get root privilege)
We now have a system with two users (I will call them olduser and newuser in this post)
Check that in Tasma>System>Login Manager the Locale Language: is US English (en_US)
To change this you have to use "Administrator Mode"
Log Out...>End Current Session and login as newuser.
As newuser start Programs>System>More Applications>File Manager - Super User Mode
In File Manager View>Show Hidden Files and surf to /home/olduser/.kde/share/config
Open kmixrc with Kwrite and change "AllowDocking=false" in "AllowDocking=true"
Save change and restart PC.
Olduser will be logged in now.
Start Programs>Multimedia>KMix and it should appear in the systemtray.
I hope this solves the problem.