Desktop Mouse scrolling issue

That little gray circle scroller thingy on your mouse, know what i'm talking about?

It's happened 1 time but i somehow managed to fix it, it jsut happened right now again and its like stuck or something.

When you scroll it makes a clickity sound, i get no sound when i scroll down, in otherwords its not picking up that i'm moving the ball one direction.

I reckon it's slipping on something since it can scroll up but not down. Anyone aware of this issue?

That's a design "feature" of the mighty mouse. Either get it swapped by Apple if you're still under warranty or ditch the mouse and buy something that doesn't gunk up.