These 3 lines caused severe trouble in Firefox, like cloing two tabs when clicking with the middle mouse button on one etc. - I was very puzzled at first, until I remembered I added this to my AutoHotkey.ini
Interesting. It works perfectly for me as coded (on a plain vanilla XP system). Could you give me any information about your specific software configuration? Your comment about the ALT-TAB function being 'tricky' leads me to believe that you have Alt-Tab "extender" software installed. As for the repeat clicks in Firefox, I am not getting that but I suppose you could just try disabling the third line of code by adding a semi-colon in front like this:
;MButton::Mouseclick, Middle ;Pass on plain mousewheel clicks
and see if that works. Also, what brand of mouse/mouse software do you have?
As a point of interest, I was expecting someone else to take this idea and run with it hence the bare-bones nature of the code. I suppose I could work on it a bit more - schedule and mightily neglected girlfriend permitting.