This started happening to me as well version 3.6.6, XP user. Started on 7-2-2010.

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.6) Gecko/20100625 Firefox/3.6.6

I wish it would open or have the choice to have it open in the same window and every time the darn page refreshes to stop bring us back. Horrible when you are reading a page and it does that . Works like that in SeaMonkey. I don't mind if both options are there. Thats what middle click can be set up for if you want it to open in another tab, but it also has the open to have it auto change to the tab or not. I have it set and it does it with the left when it shouldn't

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

You can look at these prefs on the about:config page.

• http://kb.mozillazine.org/browser.link.open_newwindow (3)
• http://kb.mozillazine.org/browser.link.open_newwindow.restriction (0)

Some extensions that you can look at:

• Tabberwocky: https://addons.mozilla.org/firefox/addon/14439
• Tab Mix Plus : https://addons.mozilla.org/firefox/addon/1122