Hi, do you get a mozilla crash reporter window? If so, please perform the following steps to give us a crash report ID that helps us find out more about the cause of the crash.

1. On the keyboard, press [Windows] The image "Windows key" does not exist. + [R]. This should bring up a Run window that contains a text field.
2. In that text field, type %APPDATA% and press Enter. An explorer window should open.
3. From that explorer window, double-click on the Mozilla folder, then double-click on Firefox and then on Crash reports. Double-click on submitted.
4. Now, you should see a list of files that contain reports. Go to View > Arrange Icons by > Modified to get the most recent files at the top of the window.
5. Open the most recent 5 files with a text editor and copy the IDs.
6. Paste each ID with bp- into the reply window on the forums.

Thanks in advance!

You can find more information and troubleshooting steps in the Troubleshoot Firefox crashes (closing or quitting unexpectedly) article.

You should try what we call a clean reinstall. That involves deleting the Firefox Program files.

• Make sure you use an official download from getfirefox.com or mozilla.org
• Do NOT delete the Firefox Profiles files and folders & do NOT use any third party uninstaller.
• Note the standard Firefox for Windows is the 32bit version even on a 64bit PC

I will include full instructions lower down.

Interesting to note my Windows Firefox is not updating to Fx50.0.1 not sure if it is a glitch at my end or whether it is an update that only apples to a subset of users for some reason.

• Release notes Fx 50.0.1 https://www.mozilla.org/firefox/50.0.1/releasenotes/
  • https://www.mozilla.org/en-US/security/advisories/mfsa2016-91/

So answering my own question it has a main fix that does not affect me but still includes security fixes I should obtain.

Clean Re-Install

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.

To do a clean reinstall of Firefox, please follow these steps: Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the close button ).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.

Please report back to say if this helped you!

Thank you.

The only crash report in the submitted folder was: bp-26d38d6a-a973-4a6a-93cb-1a38b2150227 from 2015-02-27 which must be irrelevant.

But installing 50.0.2 solved the problem for me, probably an bug in the 50.0.1 installer that was quickly fixed.