How you produced the problem;
Dragging a tab from an active window onto another screen in an attempt to create a new window, or dragging a tab from window to another. Happens without fail with five tabs open and having been using the browser for a few minutes.
How you tried to resolve the problem;
Restarting computer, clearing IceDragon, re-installing IceDragon
Any other Additional Information;
I have been able to do this for a while, but it has suddenly started producing crashes.