I have the same problem. It was in KDE 5 on PCLinuxOS as well, but there
I was able to work around it by manually editing the shortcuts file to
say "Ctrl+Shift+Backtab" instead of "Ctrl+Shift+Tab". Apparently, the
Shift+Tab was mapped to Backtab, but the Shift modifier was still
presented.
I just ran into this same problem in Kubuntu 16.04, in the process of
migrating from PCLinuxOS. The same solution also worked for me.
The command "which gnucash" revealed that I have a script in my ~/bin
that was used to work around a problem in a previous gnucash problem
(IIRC, the guile library
Public bug reported:
Trying to install Kubuntu on a ssd on /dev/sdb and hard drive on
/dev/sda, with boot loader and boot partition on the ssd. The rest of
the ssd space is to be encrypted, and all of the hard drive. Trying to
create the second encrypted volume seemed to trigger the error.
