When a mouse goes bad

I had for about 5 years now an IntelliMouse Explorer. It served me well and its size nicely fitted into my pawns. A few days ago it started to act strangely. As if the ball was full of dirt (it is an optical mouse). Also -- now I know it is related -- for a couple of days I had the issue, that Explorer would freeze. The mouse would move but nothing would be clickable. However running application would be selectable with Alt+Tab or even applications on a hotkey would launch, except task manager. The system also would not react to external drive mapping or a shutdown request.
This morning the mouse died. No mousepointer movement, finito, basta. So I replaced it with a spare (a compact optical mouse, much to small for my hands) and wonder oh wonder no more hell freezes over Explorer freezes. Mental note: even an optical mouse does age.