Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• You can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.

Your system details list shows this extension:

• SweetPacks Toolbar for Firefox 1.12.0.0

• http://kb.mozillazine.org/Uninstalling_add-ons
• http://kb.mozillazine.org/Uninstalling_toolbars

• https://support.mozilla.org/kb/Uninstalling+add-ons
• https://support.mozilla.org/kb/uninstalling-toolbars

You also have a keyword.URL that is set to the search.mywebsearch.com website. You can use the SearchReset extension to reset some preferences to the default values including keyword.URL.

• https://addons.mozilla.org/firefox/addon/searchreset/

Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).

You can check for problems with preferences and try to rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default values.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

I had this problem too. I found I could fix the problem by typing in about:config as my url. I clicked on the button that warned me of breaking something and then searched through the list until I found browser.newtab.url. Sure enough, there was a url for sweetpacks. I double clicked on in and a box popped up, which allowed me to change where I was directed to when I opened up a new tab. I haven't had any problems since.

I have the same problem. I edited the setting in about: config to the value:blank, but still get the AVG Search page when I open a new tab. That's not even my default search engine!

Try using about:blank instead of just blank.

But that's what I did enter. Didn't help.

delete a possible user.js file

• https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save#w_user-js-file-overriding-preferences

Thanks, but that file doesn't exist on my computer.

As far as not having a user,js file on your computer, did you Search Files and Folders for it or did you physically look for that file in your Profile folder?

By default Windows hides "Hidden Files and Folders" and that's where your Profile folder is located, so you won;t find it thru a "search"until you unhide those folders.
Help > Troubleshooting Information -> Profile Folder = Show Folder

Then look for a user.js file in your Profile folder.

Is the browser.newtab.url preference getting changed the next time you start Firefox?

Do you have any AVG extensions installed? Like maybe AVG Safe Search?

Thanks for the advice. I did what you said and found the user.js file and deleted it.

This time my changes to about:config were saved.

I'm still getting an AVG search when I open a new tab. Evidently, I have this add-on installed somewhere, but can't find it, and don't know how to get rid of it. AVG is my virus checker.

You can use the SearchReset extension to reset some preferences to the default values.

• https://addons.mozilla.org/firefox/addon/searchreset/

Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).