I have read the whole report and I have the same problem with Iceweasel as well as with Firefox.
I installed add-on and have to restart firefox. Firefox normally restarts but when I closed it and want to restart again, just dialog window pops up, that one instance of firefox is already running. I had to restart my computer. With the last testing version of Iceweasel it is the same. Why the dialog - One instance of Firefox is already runnig - appears? Iceweasel could not restart anymore. I have to restart my computer Cheers Zdenka
