I'm trying to use kompare, but when I go to save the file, I'm told that it could not be save. I see
couldn't create slave: "Unable to create io-slave:\nklauncher said: Unknown protocol 'file'.\n"
in the stderr, and Googling for this problem seems to always be solved by installing kio. But I have installed kio.
Originally, I was getting another error to the stderr, so I followed the instructions at Problem with KDE programs after upgrading to 15.04. That corrected some of the error messages, but this one lingers.
I'm running Ubuntu 16.04 64-bit and XFCE