Unplugging and re-plugging will resolve this. But I doubt this is how it's supposed to work.

What do I have to do?

Are you experiencing it with another usb mouse?. Could be that for some reason that trackball uses weird signalling and don't work well with MorphOS usb stack.

@crow: Difficult to find a garden variety USB mouse when all you have at hand is a netbook with a touchpad and an A1200.

Anyway, I came up with something that works for me here. I connected the trackball to the Belkin hub I got on top of the Mac mini when I bought it. And - problem gone!

[ Edited by Megander 03.12.2011 - 18:59 ]