Hello Jon.

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 theme and this one for plugins.

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

Morbus, I started in safe mode but that didn't help. I tried to open Options, nothing then a second time and FF crashed (in safe mode)

Please try reinstalling Firefox.

If that doesn't help, check if your firewall/antivirus/security suite is causing this problem. Disabling them temporarily is ok, if you don't ok untrustworthy sites.

I have exact same problem with Firefox 3.6.6. I've tried uninstalling all plugins and that did not help. I installed Firefox 3.6.3 again and then everything worked again.

Usage of 3.6.3 is not recommended, because it doesn't include the latest security fixes. If you don't want to use Firefox 3.6.6, please use 3.5.10, as it includes the latest security fixes, like 3.6.6.

Also, Berndt, did you try safe mode? Disabling add-ons in the start screen of safe mode is a sure fire way of knowing you didn't do anything wrong when disabling add-ons (extensions, themes and plugins), and it's temporary, so it's a good thing for diagnosing problems.

I have the same problem. Every ten or so minutes my the page freezes and then I get see Mozilla Firefox (Not Responding) in the address bar. FF used to be so reliable. Now it's worse than IE :( How do I fix this?

I have the same problem, but it's with version 3.6.12 (the latest at the time of this writing). Deleting downloads.sqlite doesn't help. Deleting mimeTypes.rdf doesn't help. Disabling all my addons doesn't work. Running in safemode doesn't work. Deleting my profile folder, and reinstalling firefox doesn't help. Disabling my firewall/antivirus doesn't help.

Opening the Downloads window OR initiating a download of any kind causes firefox to freeze with an hourglass.

Opening the general tab in Options also causes a freeze. This issue resembles that in this post and I think it's related. I'm going back to ff v3.6.3.

You can use the EnumProcess program written by trolly, a moderator on the MozillaZine Forums, to check what is running (e.g firewall, security and anti-virus software).
You can find more info on trolly's website: http://www.trolly.homepage.t-online.de/tools.html
The link to download the file is at the bottom of that page.
You need to run the EnumProcess program as administrator to get all info.

Do a malware check with a few malware scan programs.
You need to use all programs because each detects different malware.
Make sure that you update each program to get the latest version of the database before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy
• http://www.lavasoft.com/products/ad_aware_free.php - Ad-Aware Free
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page

See also "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked and What to do when searches take you to the wrong search website