Has it got a touch screen?
That would be my question - it sounds very much like it is set up as a touch screen device, when it's a known problem with the way the message boards work as the "hover" event is disabled on them in most modern browsers. There used to be a way to change browser settings, but that has been removed in latest browsers.
The next version of the forum software (which I am testing at the moment) behaves differently so it should work again then, but its likely to be a few months more before that is used here (some quite significant changes).