We'll see. How delightfully convenient that my profile just happened to become corrupt the moment Firefox upgraded, so surely the upgrade couldn't be a disaster. I understand your need to get off the hook, but you're just not going to do IT work if it's not evidence based.

And then, too, if you're solution to a bad program is to find a way to migrate all my data, including not just bookmarks but saved passwords and AdBlock filters, without so much as the slightest assurance it'd solve the problem, then you're going have to have an answer handy why I shouldn't just pick another browser. Got one? I thought not.

I too have this problem on two different computers, and it definitely started with the installation of the latest version. I've seen this error only a handful of times before and it was always related to something I could identify such as a forced close or crash. I've had this happen multiple times in the past several days with no common condition that I can identify. I've not changed any addons. I do note that in the new version, the old Sync is no longer valid and I had both of these computers set up for sync. I don't see how that would result in a hidden browser instance as I don't really understand the inner workings of that option. Others undoubtedly know more.

While there may be explanations with addons or others "external" factors, this is a result of the new version release and needs to be addressed as such. This is more than a minor inconvenience.

Totally agreed, and I'm still dubious from my tests that it's add-ons anyway.

It's actually decreased slightly in frequency since the first two days, although still unpredictable. It's not every browser session, but it keeps happening every day.

Can't tell if the frequency is changing. I've already had it happen this morning and it's only 9:00 and it happened several times yesterday. It happened after a short session yesterday where I did just a few specific actions. So I tried to recreate the experience after clearing the stuck process. I was able to do the exact same sequence of actions without a problem. I closed and opened FF and completed those actions without a problem several times. So clearly something else is at work.

I like FF and have used it for years. I strongly dislike IE. However, this is so inconvenient and annoying, I may need to explore using Chrome or ??

Or perhaps I should investigate rolling back to the previous version though I'm not sure how one does that. d

Exactly my experience: that is, I keep looking for a pattern to help in diagnosis and resolution, and I haven't found one, just the frustration. I don't know a way to install the previous version either. Just trying to stay hopeful.

https://support.mozilla.org/questions/997866?esab=a&s=&r=1&as=s
This is not a cure but will make it easier if Firefox locks up

I *may* have found a solution. I opened the troubleshooting option (under help) and noticed that section that details what is found in the about:config file. It shows all of the significant changes I had made from default settings. I realized looking at this, that some of these options such tabs on top are no longer used. It made me wonder what else isn't used that I may have changed and whether that could be impacting FF closing properly. I took the option at the top of the page to reset Firefox. I then when in a respecified the items important to me such as the opening page and a few other options. As of this moment (couple of days now), I've not encountered the already running error.

Of course resetting may also make changes in other areas, so I can't say for sure what may have made the difference. I just know that so far, it appears to be working. I'll let you know if that changes, but two days without an error that had been cropping up multiple times a day is encouraging.

Good luck.

Scary thought, as I'd have to reinstall immediately the extensions I need, especially ftp, and configure them as best I can -- assuming I have my ftp passwords somewhere, say, and won't lose years of working with specific lists and personal choices in AdBlock. But since Firefox clearly messed up unforgiveably, I may be stuck trying it. OTOH, if I have to start from scratch after all, why stick with Firefox at all?

If you want, install these add-ons. They will be a great help.

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences

Very interesting, and sounds helpful. Thank you.

Not sure of that. I had re-enable my Norton's extensions, but did not have to reload them or any of my add-ons. Perhaps the reset is not the same a wiping it clean to a bare start. Literally the only things I had to do were to reset my home page, make a few minor adjustments to options I'd changed along the way, and re-enable the NIS extensions. I don't have AdBlock, so I can't comment on that but I saw no evidence that anything other than Firefox options were reset.

Thanks. I was going by a Mozilla page description of what reset does, but I'm totally open to finding out for myself.

This link can answer some of your questions; https://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-most-problems

Yes, and as a matter of fact it's exactly the page I was referring to. (Note that it says reset removes extensions.)

Yes, reset removes extensions. Plugins, however, is different. Each time Firefox starts, it checks your system for them. Things like passwords, history, and bookmarks are copied to the new user profile. Most options are reset to factory default.

Really, honest, I wasn't worried about plug-ins like Adobe Acrobat.

And come on, think about it. If plug-ins like Acrobat, Quick Time, Real Player etc. that respond to file extensions had to be replaced, you might as well forget your browser, wipe your hard disk, and spend a few days reinstalling your OS, for goodness sake.

I'm sorry, but I've been a supporter of Firefox ever since I had to migrate from Netscape, but now I wouldn't recommend it to anyone.

Well, guys, that was not a good experience. I reset Firefox this morning. While I've lost a lot (such as which sites will remember cookies), and while I haven't yet installed any add-ons except for FireFTP, already I'm getting the error more than ever. So I'm afraid that's not the solution.

Okay, guys, I think its time to get dirty.

Run several or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

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