Instead of removing the whole ~/.kde directory, I had to delete these lines in the ~/.kde/share/config/kdeglobals file:
[General] BrowserApplication[$e]=firefox.desktop XftHintStyle=hintmedium widgetStyle=qtcurve
After that, all worked as expected.
Instead of removing the whole ~/.kde directory, I had to delete these lines in the ~/.kde/ share/config/ kdeglobals file:
[General] ion[$e] =firefox. desktop hintmedium
BrowserApplicat
XftHintStyle=
widgetStyle=qtcurve
After that, all worked as expected.