This is a bit odd: When I enter fullscreen mode with typewriter scrolling turned off and no scrollbar, I cannot scroll with my trackpad. If I turn typewriter scrolling on and off, it works again; it also works if I have any kind of scroller turned on (but I don’t want to). The scroll buttons on my external trackball work like normal, so it only seems to affect the trackpad.
I use Scrivener 2.2 and Snow Leopard 10.6.8 on a MacBook.