While kdesu is 'hanging', watch it with top or htop to see if it is getting any cpu time, swapping, allocating a bunch of memory, waiting on other files, etc.
Also, try 'strace kdesu dolphin' and watch what files are being queried just before and while the hang is going on (if any). This could give you clues about what to search for next.
It used to be that after some upgrades to KDE or KDE programs you had to delete the "old" config settings for the program under ~/.kde and/or ~/.config for the new version of the program to work correctly. I haven't had to do this in a while, though.