I run into this more often than I should.
Apparently closing Firefox doesn’t always mean it’s not still running.
Click on the picture to enlarge
It happens less often now than it did in older versions.
From experience it seems to occur when a badly-written Java applet crashes Firefox.
I have to say I haven’t had this happen since the early versions of firefox, pre 1.0.
Yeah… from time to time, with one or another set of extensions, firefox just crash and stay there.
Spamihilator does the same…
I wish I could know what generates that…
While FF is running a file named “parent.lock” is created when FF is shut down if there is a problem this file will remain.
If there at FF shut down. Stop the FF process and delete “parent.lock” file.
I was having a similar problem with FF and this fixed it for me. Good luck this can be a real pain Bob.
Hi bob3160,
Here you can find a cure for your problem: https://bugzilla.mozilla.org/attachment.cgi?id=249012
Cut the “nsSessionStore.js” part there and paste it into your components folder of the browser as a JS file.
Tell me if this undercuts your problem,
polonus
But did you do once or you need frequently to do that… can you imagine what does cause this?
Polonus, I already has a nsSessionStore.js file into components folder…
I’m not self confident that I should change anything to a new version.
I have a fair idea what causes this. Poorly written addons and as FwF has already mentioned badly-written Java applet etc. Yes I only did this once as “parent.lock” has not reappeared in my profiles folder when FF is shut down.
Something else that my help is
FF tweak about:config
config.trim_on_minimize set value to true
If you don’t have the preference, just add it
Right click anywhere in the preference list select New --Boolean
Preference name should be config.trim_on_minimize value set to true
Something else that my help is FF tweak about:config config.trim_on_minimize set value to true If you don't have the preference, just add it Right click anywhere in the preference list select New --Boolean Preference name should be config.trim_on_minimize value set to true
Thanks tednelly, it was set to false and has been changed. 
Now we’ll see if it makes the annoyance disappear.
Well to the annoyed,
Flock does not have this specific annoying FF problem, and is known to be much more stable than it’s cousin.
There is still another annoyance I found in FF, that is I need to customize toolbar again, because installing a certain extensions after start-up removed my search-engines from the toolbar. The Febe extension worked good for me because you can reinstall all variables from the file where you backed it up. So completely reinstalling the browser is less of a problem, reinstall Febe and the lost browser and all its settings, extensions, etc. is restored in a jiffy. You can get Febe from here: http://customsoftwareconsult.com/extensions/
But I think at the root of the trouble is browser.js
polonus
Polonus, what do you have to say about tednelly`s solution?
He doesn’t have to answer… 
Sorry but that fix didn’t work for me.
I backed up (renamed) the old “nsSessionStore.js” file and replace it with the one Damien suggested.
I then again crashed Firefox, and ran CCleaner.
This time the surprise was a pleasant one.
The new code apparently fixed the problem.
Thanks Damien.
By the way, your speedup is still speeding things up.
Hi bob3160,
More or less did as I expected. I did a search on the problem, spade through the bugzilla bug patches, then came up with something that could close it down when it found a false. And apparently it did.
At home I have fed browsers all sort of code to see how it would react to it, so I learned a couple of things during the process, my friend. Just had to wait a bit for my reaction, because I had to try out the PicLens 1.5.4 add-on for FF with google images and yahoo. It makes a gallery on screen format, and the photo’s are presented at their best. Beautiful add-on, friends. But Bob back-up all what you have in your FF browser with the Febe extension, and you can restore anything from there, so you can never loose a specific profile, even if the browser crashes. Nice I could be of any help,
your anti-malware friend,
Damian
Ok, he doesn’t ‘have to’, but I’m asking his ‘opinion’ as a favor…
Hi Tech,
Sure will to the best of my abilities. P3t3R meant well, but what he proposes has to do with CPU consumption, and older problems for which you had resize the browser window to make it consume less. This is in various textbooks, but this was not the crux of the problem our bob3160 was struggling with, it was not a conflict of add-ons and browser but a known bug in the way the browser executable keeps running in Task Manager reacting to something it should not react to, that is what the patch I suggested to bob3160 actually does: ignore a false. If P3t3Rs’ story was valid a restore of my profile folder with the Febe extension would have cured bob3160’s problem, it did not.
I hope this helps to give you an idea of what happened here,
pol
Hi Damien,
Unfortunately, Febe is the program that kept crashing Firefox on my system.
I’m about to uninstall it now.
Hi bob,
Maybe you have too much options running, then it will not function with me either.
Glad your FF is still up and running. But if it is not doing what it should take it off.
polonus
Which was your backup frequency?