This is a rather old bug, but I still came across with it on an up-to-date Debian Stretch (on March 2019). In my case it was caused by TeamViewer, after uninstalling it (and rebooting), the problem was gone.
So for other people that may come across this issue, I'd like to emphasise that you really should have a look at this link posted before: https://bugs.launchpad.net/inkscape/+bug/418242 And check if you're running any of those programs. After uninstalling it you may need to reboot to get it completely sorted out. Best regards, Bruno
