Firebug opens for every page that loads

[H]

Hi,
I am having a problem with Firebug: it works perfectly, but its docked
window opens for every page that loads; be it a new tab or loading a
new url over an already open window, even if I closed Firebug
previously. Is it there any way to disable that behavior?

I remember it used to start "minimized" with the green icon on the
bottom of Firefox window, turning into red when JS errors happened.
After recompiling Firefox in a Firebug stopped working, and I found in
this forum that I needed the "mozdevelop" USE flag. Recompiled, and it
started working... in the way I described. Anyone know where is that
configured? The extension itself does not have a Config window...

Thanks,
Hernan.