Running FF 3.6.13 on W7 - Clean install on new machine. Ad Block Plus is the only add on for FF and the only other application that affects running applications is Avast AV Free version.

Sometimes when I choose to right click and open in a new Tab, the new Tab will open as it should leaving me on the same page - sometimes it won't - it will move to the next most recent tab that was opened - not the tab that was just opened. Sometimes it will allow me to open multiple tabs without any issues - and other times it never works without shifting which tab is the active tab. It seems to work 100% of the time on Google - and close to 0% of the time on FaceBook - other sites seem to be in between.