This is more of a tip than a problem. The better kind of post to make, of course
I had problems with Yast2
refusing to launch any sub-windows (install software, installation sources, etc). No apparent error messages appeared, but it just did not work.
It appears now that this was due to the fact that there were more than 32,000 'temporary' directories called /tmp/YaST2-something in my /tmp folder
Upon removal of those YaST2 started working again. Perhaps something that could be useful to know and was hard to find.
PS. Cleaning out all kde related stuff out of my /tmp directory also ended up fixed a more recent problem in which I could not get KDM
to start upon startup, even though manual starting of KDE itself (using startx) did still work...