I have the same problem on Ubuntu 12.04 amd64

I have posted this as a bugzilla report. I new to that so edit the report as needed to make it more accurate.

https://bugzilla.mozilla.org/show_bug.cgi?id=800008

What started all this was the fix for Bug 277079 - "Close other tabs" should always warn about closing multiple tabs which took effect in Firefox 16.

nlinecomputers, Your bug was resolved as a duplicate of Bug 772319 - No option to disable the "Close other tabs" prompt. This will be "fixed" in Firefox 18 by offering a new "hidden" preference that can be set in about:config. From comment 31:
To get the functionally back you'll have to install Firefox 18, typing about:config in the address bar, search browser.tabs.warnOnCloseOtherTabs and change the value to false.

You're treating your users like children. I want to be able to close multiple tabs without an aggravating and needless reminder and I don't want to have to make "hidden" config changes to restore what used to be so simple.

This is an irritating and dumb move.

Looks like the new browser.tabs.warnOnCloseOtherTabs preference, (which can be toggled from true to false in about:config to turn off the warning) will be available in Firefox 17, which ships on 11/20/2012. It will also be available in Firefox Beta in Firefox 17 Beta 4, which isn't out yet but should be soon, for those users who don't want to wait for Firefox 17 final. _{ref: bug 772319}

Funny thing:

As opposed to the thread starter's issue, now the exact opposite is the case. Neither the “Warn me when closing multiple tabs” option nor the browser.tabs.warnOnCloseOtherTabs preference do have any effect anymore in FF17.

Update: setting browser.warnOnQuit to true now does the trick and brings browser.tabs.warnOnCloseOtherTabs back to functionality again.

This fix works, but once it's applied the option to have FF warn the user when closing multiple tabs no longer works -- that is, checking the box to receive such warnings does nothing.

@RDCollins: This is only the case when you are using Tab Mix Plus – hence I didn't contribute any further on this subject here, as it is not a Firefox bug.

The issue concerning TMP is already discussed in the following thread: [Firefox 17.0 doesn't warn me when closing multiple tabs]

I have no idea what you're talking about. I do not use Tab Mix Plus -- it's not installed and I've never even heard of it before.

Whether the failure of FF to close multiple tabs without the warning notice is a bug or not depends, I suppose, on one's definition of "bug" -- but whatever you call it, it's a problem that did not exist in earlier versions of FF, and it should be fixed whether you like it or not.

Hmm, that's interesting. Sorry for the assumption made above, but to date this issue only surfaced when having TMP activated at the same time ...

BTW, you really should have a look on that, it ranks as a must-have add-on ;)

As for FF17 alone, I could not reproduce the faulty behavior without TMP, so I have no idea what you are talking about ... no need to get caustic, though.

Alas, I can't re-check it, as I'm back on 16.0.2 until further notice of bugfixes.

In my case, I checked the "Warn me before closing multiple tabs" option. It worked fine in the beginning. And "Warn me before closing multiple tabs" will never work again once I used panorama (tab groups) function one time (one time will do). This case is for both firefox 17,18. And it happened on win7 64bit home premium and win xp.

What's your setting of browser.warnOnQuit ?

Is it true as it should be, or false so that it doesn't work anyway?

To FFmurphy, my setting, "browser.warnOnQuit" is true, the default value.

If you have an extension like Tab Mix Plus that overrides the build-in Firefox prefs then only changing the settings in TMP can work.

You can test this by temporarily disabling TMP.

To cor-el, my firefox only installed noscript extension. And I have tested firefox in safe mode. the issue was stilll there.

So you guys don't encounter this issue?

cor-el, if mizuc was using TMP with FF 17 his setting of browser.warnOnQuit would be set to false and locked on false, as clarified in the other thread ... So his issue is apparently different.

I am on FF 17.0.1. Unlike what posters have said above this issue is NOT resolved. FF 17 did not change this at all.

The checkbox "Warn me when closing multiple tabs" has no effect checked or not. The about:config line browser.tabs.warnOnCloseOther does work. But why the heck do we need to use this? Why is there a config checkbox in the standard configuration setting THAT DOES NOT WORK?

Why do you have to do a about:config trick to get functionally that used to be a standard part of the system? And why is a dead checkbox still in the code?

I am told that is by design to simply the interface. How is having broken checkboxes and having to dive into cryptic about:config setting SIMPLIFYING THE INTERFACE?

This is stupid, truly jaw slacking stupid programing.

To FFmurphy, I have tried to reset FF 17.0.1 (help->troubleshooting information->reset firefox). And the issue remains there. (It seems that only reinstallation can restore the function...if you don't use panoram again.)

Since even reset Firefox can't restore the "warn me before closing mutiple tabs" function, I thought this was a general issue that most people will have. (if you use panorama function) Yet it looks like you guys don't have this issue. It is strange.

I saw an useful answer by Fanolian on Moztw.org forum.

The panorama issue seems related to this one. https://bugzilla.mozilla.org/show_bug.cgi?id=709579 Which mentioned "Closing multiple tabs warning doesn't work correctly when the "Show my windows and tabs from last time" option is selected".

After installing firefox and using panorama the first time, the "When Firefox Starts" item will be forced to be "Show my windows and tabs from last time". (Is this a right reaction?) Thus, after using panorama, consequently, "Warn me when closing multiple tabs" doesn't work.

Still an issue in Firefox 19.0.

I do not want to be warned when I use the "Close Other Tabs" feature. And forcing users to modify the "about:config" page for such a simple option looks like a bad idea. "about:config" is an Admin tool, isn't it?

Firefox is great, but this issue is so annoying that it made me register here, for the first time ever.

Please make the "Warn me when closing multiple tabs" option do what it is supposed to do.