I just had this exact same problem, except that I did not only have one .config/kglobalshortcutsrc.lock file, but a lot of them like:
kglobalshortcutsrc
kglobalshortcutsrc.lock
kglobalshortcutsrc.lock.rmlock
kglobalshortcutsrc.lock.rmlock.rmlock
kglobalshortcutsrc.lock.rmlock.rmlock.rmlock
kglobalshortcutsrc.lock.rmlock.rmlock.rmlock.rmlock
kglobalshortcutsrc.lock.rmlock.rmlock.rmlock.rmlock.rmlock
... and so on ...
I just had this exact same problem, except that I did not only have one .config/ kglobalshortcut src.lock file, but a lot of them like: src.lock src.lock. rmlock src.lock. rmlock. rmlock src.lock. rmlock. rmlock. rmlock src.lock. rmlock. rmlock. rmlock. rmlock src.lock. rmlock. rmlock. rmlock. rmlock. rmlock
kglobalshortcutsrc
kglobalshortcut
kglobalshortcut
kglobalshortcut
kglobalshortcut
kglobalshortcut
kglobalshortcut
... and so on ...
After deleting these files I could login again.