Prevent auto-loading of tabs in Firefox when starting browser

At the time I write this, this is a known issue:

http://garyr.net/tmp/forum/viewtopic.php?t=15821&p=55432

The only workable solution I've found is to disable session management in Tab Mix Plus*, enable the Firefox setting to only load tabs on demand (under tools -> options -> tabs -> "Don't load tabs until selected"), and, if you still want similar (probably better) Session Management functionality, install the Session Manager extension --

https://addons.mozilla.org/en-US/firefox/addon/session-manager/ --

This extension has an equivalent setting under Tools -> Session Manager -> Session Manager -> General -> Saving and Restoring -> "Restore Tabs on Demand."

*As I've just installed the Session Manager extension, which modifies Tab Mix Plus' options interface, I don't recall exactly where to do that.

The "Don't load tabs until selected" option in Firefox is enabled by default when "Show my windows and tabs from last time" is selected. This is in Preferences > General:

You can change the restore behavior by going into about:config and changing the "restore on demand" option.

If it's not working then open multiple tabs, disable all of your plugins and restart your browser. Check if it's working. If it is then enable one plugin and restart. Check if it's working. If it is enable another plugin, restart and check again.