well i havent experience it but then thats cause i have single window enabled, have u tried that?
Not sure which such entry you are asking about.
I do have Firefox, Tools, Options, Tabbed Browsing set for using a tab in the current window and, of course, TBP set for links to open in a new tab in the current window.
Ironically, when I clicked on the link in the email to which this is a response, the link opened in a new tab in the current window.
Just a few moments later:
Hah! Found the problem: If the first and only tab in Firefox is blank, then a link from another application, such as Thunderbird, will cause the link to open in a new window.
I was suspicious while writing the first part of this reply, because I had something in the first Firefox tab. So, after posting the reply, I closed both the tab in which my reply was posted as well as the first tab.
I then returned to TB, clicked on the link, and got a new window. I closed that new window, put something into the first tab in FF, clicked on the TB link once again, and this time the link opened in a new tab in the same window.
(On a nosy personal note: I recall your stating, perhaps on MozillZine, recently, that you are about to return to college. Might I inquire as to where you are enrolled? I teach college-prep kids, so I'm always interested in such matters.)