Well, i'm no expert at this, so be careful when trying my advice.

1. In your URL bar type 'about:config' (without the ' ')
2. Click to agree
3. Filter for browser.warnOnQuit and change the value to false.
4. Filter for browser.showQuitWarning and change the value to false.
5. Restart Firefox

I'm not sure if this will work for you, or if there is an easier way, but worth a try.

Hi. 1. In your URL bar type 'about:config' (without the ' ') — This got me in OK. 2. Click to agree. — I was not asked to do this. 3. Filter for browser.warnOnQuit and change the value to false. I found this in the list ok, then went looking for No.4, before making any changes. 4. Filter for browser.showQuitWarning and change the value to false. — I could not find this in the list. 5. Restart Firefox. — Not being able to find No. 4 in the list, I did not make any changes, so I back-peddled instead of restarting.

Many thanks for your help. David.

Additional info.

I spend quite a lot of time on the internet, and somehow that slows down my Apple iMac computer along with most of the programs that I have installed, especially AppleWorks 6, so around every 8 to 9 months I trash and reinstall both the system and AppleWorks 6. This always fixes the problem. Everything is back to running at full speed again, but this is the first time that Firefox has played up, so the problem could be in one of the updates Firefox has put out over the past 9 or so months. — Just a thought. David.

Glad it all worked out in the end. Some of my instructions may not have applied because you are using an old version of FF and Mac OS X. I am on 10.7.3 and FF 10.0, so could only work with what i had :)

Hi. After a few more hassells, I decided the best thing to do was to trash Friefox and reinstall. Lost all my history in doing so, but everything is working as it should now. Firefox closes now without any problems when I ask the computer to shut down.

Thanks for all the help. David.

No problems, glad its all sorted.

Its a shame to lost your history, hopefully you recovered your bookmarks though. If not, I recommend trying something like FF built in sync, or for older versions an add-on like Xmarks to backup your bookmarks.