Just download the latest version off of getfirefox.com and install it over your current install. No data will be lost, don't worry. That should fix the problem.

If the problem persists on future updates, it's possible that you are having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?

Whenever you have a problem with Firefox, whatever it is, you should make sure it's not caused by one (or more than one) of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode (don't forget to select Disable all add-ons when you start safe mode). If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and themes and this one for plugins.

If you need support for one of your add-ons, you'll have to contact its author.

If the problem does not disappear when all add-ons are disabled, please tell me, so we can work from there. Please have no fear of following my instructions to the line, as all can be easily undone.

See also http://kb.mozillazine.org/Software_Update (Software Update not working properly)

Thanks for the replies. I updated to 3.6.8 and it is no longer having the issue (I wasn't aware another version was already out, so thanks for the heads up)

Sorry- hit the solved button next to the wrong post, hadn't seen the second reply pop up!

This fix, to download and install the latest ver, 3.6.15, does not work. The install wizard hangs up because it thinks there is another copy of Firefox running. And now Firefox will no longer open at all. Uninstall wizard also hangs up at exactly the same point, so will not let me uninstall and reinstall. Previously, while running 3.6.13 I had been getting prompts to upgrade, and the auto-upgrade hung up similarly --"another copy of Firefox is running, please close" or similar words. So now I am locked out of Firefox altogether. And Live Chat is closed. Help, please!

Do a clean (re-)install:

• Download a fresh Firefox copy and save the file to the desktop.
• http://www.mozilla.com/firefox/all.html
• Uninstall your current Firefox version and remove the Firefox program folder before installing that copy of the Firefox installer.
• Don't remove personal data if you uninstall the current version.
• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• It may not be necessary to create a new profile, so first try if it works with your current profile and if not then create a new profile.

You do not need to create a new profile, that is not necessary for this issue

Your bookmarks and other profile data are stored elsewhere (not in the Firefox program folder) and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.

Thanks for prompt reply, but I have tried to uninstall Firefox, (and to open in SAfe Mode, and to force it to start via the command line.

Uninstall will not work because the Wizard gives the same error message, "another copy running" or "close Firefox before proceeding" or words to that effect. But no Firefox is running, there is no Firefox in Task Manager. How do I get past the erroneous "another copy running" obstacle so I can uninstall?

Just got live-chat help and the problem was resolved: Task Manager, Processes tab, where I did not know to look -- showed firefox.exe. Getting rid of that eliminated the problem.

Hoe do I get Firefox to NOT update... update works but 7.01 is a piece of shit and does not work.