Unsure if I should start a new thread on this, but "Microsoft Hardware USB Mouse" recent installation of Intellipoint 8.1 software caused some bizarre behaviour on my machine when using a different mouse subsequently.
Applications were reacting as if I were slowly scrolling my wheel down. That is to say the vertical scroll bars were scrolling automatically; same with sliders when vscrolls weren't presented (on, for example, the Mouse control panel). This happened on browsers, java apps, Word, control panels.
Uninstalling Intellipoint software fixed the problem.