Plasma workspace error

[lafeber-dumoleyn2]

Since the last update of Kubuntu I get an error with Plasma workspace 
KDE DRKonqi Kdeinit4 PID 1478 signal: segmentation fault. The desktop is 
completely black.
Via Google I found a solution on a forum: rename .kde4 folder. But I 
cannot find a .kde folder. There is a folder with the name kde4 in /etc 
and /usr, but not .kde4.
I can open any program I know the name of with Alt+F2, but I cannot 
reach them through Start (which does not show).
When I start Kubuntu in Recovery mode the prompt is root at myPCname. When 
I type Rename .kde4 kde4Bup I get an error message.
Can anyone help me out?
Hannie
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