The issue is probably caused by one of your add-ons. Restart Firefox with Add-ons Disabled to check if that's the case.

• Diagnose Firefox issues using Troubleshoot Mode

If the problem goes away in Safe Mode, you can either try to determine which add-on is to blame, or you can Reset Firefox and get rid of them all.

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems
• Refresh Firefox - reset add-ons and settings

I have this exact same issue.

• I tried safe mode.
• I tried resetting Firefox.
• I uninstalled and reinstalled multiple times, both with keeping my profile and without - both ways don't solve the problem. I tried the install stub file and the full install file. Neither solve the problem.
• I ran ccleaner to clean out the registry between installs. No help.
• I manually renamed all the plugin files to eliminate plugins being the culprit, but my colleagues have the exact same plugins installed and they're not having issues on the latest version. Note I'm not talking about addons - that possibility was eliminated by reinstalling with a new profile so that's not it
• I uninstalled WebRoot (a small, simple rootkit detection software which banks usually offer you free of charge to ensure security while you're logged into their online services)
• I even went so far as to uninstall Chrome (since Chrome has a Google Update plugin which shows up in Firefox for some reason, so I thought it might be a conflict) and even Adobe Flash Player! Nothing.

The only thing that works is if I roll back to Firefox version 28, the last version before all the layout changes, and it's not really an option since all the plugins I need don't support that version anymore.

• Can't open the hamburger menu.
• Can't customize. Typing about:customizing into the address bar opens a blank tab
• The Firefox home page doesn't work (as in, Firefox opens a blank tab instead of the home page, and if you click the home button and type something into the search bar and hit search, nothing happens)
• The firefox message that pops up just below the address bar, for example when you're downloading an add-on and it shows the download rate, doesn't work.

I'm at a complete loss. If anyone has any more ideas I'd be glad to hear them. Alternatively, I think the devs should hear about this. I'm happy to provide whatever debug or logs they require.

No surpise that no one knows how to fix this. Anyone know how we get in touch with the dev's?

It worked for me when I switched back the desktop theme to a Windows standard theme and restarted Firefox...

yeti-

YES! That was it! THANK YOU! Everything's back to normal - awesome!