CONFIRMED.
H3D, Octaga, Instant, Vivaty, freewrl.v3 
- isOver working (hides sphere when pointer over sensor box, sphere shows when off the box sensor)
freewrl.v4
- no isover activity

I remember there were issues on a touch screen - like a mobile device - and remember working on that so a finger drag could be used in the isOver sense. I put a button on the menu bar called HOVER ^ (use ? button to show meaning of buttons when you press them). With HOVER turned on, if I left-mouse drag on the box and -holding LMB left mouse button down- drag off the box then the sphere shows, like the isOver = false in the other browsers and v3 of freewrl.
-Doug