I think the title mostly describes it. I'm using Firefox 18.0 and Zotero 3.0.11 under Linux Mint 14.1.

All of a sudden, I notice that clicking a web link in any application other that Firefox (which is my default browser) -- for instance, from my email client -- causes Zotero for Firefox to open a fullscreen window, rather than opening it in Firefox itself, as it use to. So, for instance, when I click a link in Thunderbird, I would normally expire Firefox to open the link, but instead, what opens is a new Firefox window, which then opens the fullscreen Zotero window (as if I'd opened a new Firefox window and then typed "zotero://fullscreen" into the title bar). The Zotero fullscreen window doesn't seem to handle the link in any way; it simply appears.

What I really want to happen, of course, is that Firefox simply opens the link in a new tab.

I've tried looking at Firefox's "Applications" tab in the Firefox preferences dialog shows that the handler application shows that the handler for "http" and "https" is "Use Zotero in Firefox (default)." I've tried changing it to "Always ask" and to the location of the Firefox executable (/usr/bin/firefox on my system, according to "which firefox" in a terminal), but neither of these makes a difference. Notable, "always ask" doesn't result in me being asked. I'd simply delete the http and https entries from the helper applications list if I could and see whether that helped, but there's no "delete entry" option on the applications list.

Yes, I could simply right-click on a link in Thunderbird, copy the link location, alt-tab to Firefox, hit ctrl+T to open a new tab, click in the address bar, then hit ctrl+V and Enter ... but this is a REAL hassle if I have a lot of links to open (as I often do, since my department constantly bombards me with email).

I recently checked "always check to see if Firefox is the default browser" in the Firefox preferences, but there was a lag between when I did this and when I noticed that links were opening with Zotero. Unchecking it doesn't help, either.

Here's a video illustrating the problem: http://telly.com/0J8120. You'll notice that a debug output is created during the video; the debug ID created during the video is D1754573690.