Middle button doesn't invert selction any more

[Leo]

That may mean the mouse drivers are configured to map the middle button to something else.

This is about Logitech, but several other drivers are similar as well:

How to: Make Logitech Mid/Back/Forward buttons work in Opus

By default Logitech's SetPoint drivers assign the Middle, Back and Forward mouse buttons to non-standard functions which don't work in Opus and a number of other programs. To make the Middle mouse button work in Opus -- so that you can use all three…