Okay, I just got a new computer, running an OEM of windows Vista, and I got FF 220.127.116.11. I also use a Logitech G5 Laser mouse, with a thumb button you can set to various tasks in various programs. I like to set this to middle-click in FF, because my mouse wheel does not middle-click well. Now, I got it to middle click, and it opens a new tab, but is also backs my current tab up one page. I have both FF, and my mouse set up like on my old computer. FF is running the Tab Mix Plus extension, and I have SetPoint installed for my mouse, and everything is updated to it's most recent version. I've tweaked options to no end, and this still happens. Anyone have any ideas?