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.

Did this fix your problems? Please report back to us!

Type about:config in Addressbar and search for browser.newtab.url and modify the value to about:newtab

Remove ZoneAlarm

• http://www.wikihow.com/Completely-Uninstall-Zonealarm-Free-Firewall

In order to uninstall a possibly unwanted extension, please do the following:

1. From the Firefox window click the Firefox button at the top left and select Add-ons, or, if the Firefox button is not shown, click the Tools menu and click Add-ons.
2. Once the Add-on Manager has opened in a new tab, click the Extensions button on the left side of the window.
3. You should now see a list of your installed extensions on the right side together with buttons on the right side of each extension.
4. To remove an extension from Firefox, simply click the Remove button. You should see a message that informs you about the successful removal of the add-on.
5. Note that some add-ons require a Firefox restart to be removed completely. To perform a Firefox restart after the add-on removal, click the Restart now link in the message.

You can find further information about uninstalling extensions in the following articles:

Disable or remove Add-ons

Remove a toolbar that has taken over your Firefox search or home page

It's not malware, it's enemy action by ZoneAlarm, which insists on doing this. It isn't browser.newtab.url either, that's still about:newtab - must be somewhere else. I've fixed this before, but can't remember where exactly

It's not malware, it's enemy action by ZoneAlarm, which insists on doing this. I've got rid of the add-on, but the new tab still comes up with the thing. It isn't browser.newtab.url either, that's still about:newtab - must be somewhere else. I've fixed this before, but can't remember where exactly

check this thread: https://support.mozilla.org/en-US/questions/960332

OK guts, fixed it! The crucial action was : in about:config, find browser.download.lastDir, and reset it - ZoneAlarm (Checkpoint) had modified it!.