In windows, I often drag a link out to my desktop from the browser's address bar. This creates a url shortcut that I can copy to a flash drive and then open it on another computer. I tried opening one of those shortcuts in Lubuntu, and firefox asked me if I wanted to make firefox my default browser (which I already did when I first installed). When I answered the dialog, it started opening one tab after another - no way to stop it. I have ff configured to open with the tabs from the last session, so even if I close ff and restart it, it asks me again if I want to make it my default browser, and no matter what I answer, it starts opening tabs rapid-fire, and I can't do anything to regain control of the browser.

Is this a bug in Ubuntu Firefox? How do I regain control of firefox?