Could I suggest turning off some of your add-ons. Try disabling ALL nonessential or unrecognized plugins and extensions on the Add-ons page. Either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Plugins. If you do not think you will use it during the next 48 hours, set it to either "Ask to Activate" or "Never Activate".

In the left column, click Extensions. Then, if in doubt, disable.

Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Hopefully this will bypass any issues caused by those add-ons and we can consider other factors.

As part of this process you may need to remove or edit the user.js file that is overriding your settings at startup. This article has more information on chasing that down: How to fix preferences that won't save.

Note that some extensions can add to this memory usage.

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem.

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