Try running Firefox in Diagnose Firefox issues using Troubleshoot Mode. If it functions properly in that configuration, then one of your add-ons is the culprit.

Still nothing :(

If you use Google as your home page, I'd suggest doing the following.

• Go to google.com
  
  
• Click the orange Firefox button and go to Options | Options | General.
  
  
• Make sure it says "Show My Homepage" in the first dropdown menu.
  
  
• Click the button called "Use Current Pages" to set the homepage to the one you have on the screen.
  

If you prefer a different search engine, substitute that for Google.

https://bugzilla.mozilla.org/show_bug.cgi?id=637639#c5
if dom storage is disabled when the profile is upgraded, about:home remains broken even after dom storage is re-enabled

https://bugzilla.mozilla.org/show_bug.cgi?id=637561
about:home does not check for disabled dom storage (null localStorage)

1. You need to make sure that domStorage is enabled.
Type about:config in the URL bar and hit Enter.
If you see the warning, you can confirm that you want to access that page.
Filter - dom.storage.enabled = the Value should be True
If not, double-click that pref to toggle it to true.

2. Then right-click this pref and select Reset after enabling dom storage
browser.startup.homepage_override.buildID

Still nothing, unfortunately

Try to delete the file chromeappsstore.sqlite in the Firefox Profile Folder

• http://kb.mozillazine.org/Profile_folder_-_Firefox

Help > Troubleshooting Information > Profile Directory: Open Containing Folder

Do you have AVG Safe Search installed? That blocks use of the Enter key after typing in a search.

If so, disable it by clicking the Firefox button, go to Add-ons, then Extensions. You should find it in there.

If you don't have that, are you using McAfee Site Advisor? Disable that via the same route.

I have Kaspersky site advisor, but it's been disabled since I upgraded. In fact, the browser still behaves the same in safe mode. I deleted the .sqlite file as well, but still no luck. :(

Try creating a new Profile. See Profiles - Where Firefox stores your bookmarks, passwords and other user data

If that works, you can recover your passwords, add-ons etc., from the old profile and transfer them to the new one. See Profile Manager - Create, remove or switch Firefox profiles

You can try "Reset all user preferences to Firefox defaults" on the Safe mode start window.

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

Wow, thanks the-edmeister, had exactly the same problem this morning, I was stumped, this solution work perfect.

Thanks, much appreciated for this knowledge.