Source: askubuntu.com
Ubuntu has an error reporting system called apport which tries to catch all program crashes in the background and report them to help the developers.
It seems that some reports get stuck and try to resubmit, but disabling apport is not a desirable solution.
Open a terminal and remove all old crash-reports that might exist in the crash -report directory:
sudo rm /var/crash/*
After a reboot the popups are gone.
If you don't want to reboot, you can close all open popups with:
killall system-crash-notification
(Any further new pop-ups still should be investigated. If you want to see the details,
look in /var/crash/ for any new reports)