Unfortunately, your crash report was dated March 17th and relates to Firefox 37.0 beta, so I'm not sure it really identifies the problem you are having today with Firefox 38.0 beta. If you do not have a more recent crash report, could you describe the situation in more detail?

Also, could you test whether the same problem occurs in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any less crashy?

Note that your System Details list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file is only present if you or other software has created this file and normally it wouldn't be there.

You can check its content with a plain text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

You can delete the user.js file if you didn't create this file yourself.

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

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox