Other contributors were talking about some of the issues with add-ons that did this when the Firefox 29 upgrade went live to all users.

I'm curious to know if you have some of the add-ons that cause this. Can you send me your troubleshooting information from the Firefox installation that's having issues? This is a good part in troubleshooting.

• Navigate to about:support via Address Bar
• Click the button that says Copy text to clipboard
• Now, go back to your forum post and click inside the reply box. Press Ctrl+V to paste all the information you copied into the forum post.

While you are doing that, Can you try to start Firefox in Safe Mode to see if Firefox works properly with no error? You can start Firefox in Safe Mode below:

• Windows/Mac: Go to Help > Restart with add-ons disabled
• Linux: Run firefox -safe-mode in the Terminal/Konsole

If Firefox opens up fine with no problems, it's probably one of your extensions that's causing the issue. You can re-enable your add-ons one by one until you find the one that causes the issue upon being re-enabled.

You can check for problems caused by a corrupted localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

You can also try to reset the browser.uiCustomization.state on the about:config page via the right-click context menu.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

thanks, i was locked out of doing anything till i was able to start safe mode by opening firefox with shift key depressed. was able start from beginning. best wishes, don

Javascript Command 1.01 extension caused this for me. I had a green transparent background that matched the Windows Aero titlebar. On exiting Customize the window remained blank until I restarted Firefox. It is fine with Javascript Command 1.01 disabled.