Hello Iqbal.

You may be 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 coming from 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 and select Disable all add-ons. 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. You can troubleshoot plugins the same way.

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

This issue can be caused by a plugin or an extension that is not compatible with Firefox 3.6 and isn't working properly anymore. A toolbar like the "ZoneAlarm Spy Blocker Plugin Stub for 32-bit Windows" and other toolbars like "Ask.com" or "My Web Search" can cause this issue.

See http://kb.mozillazine.org/Issues_related_to_plugins#Identifying_installed_plugins

See also Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems and Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems