Is the limit still fixed at 40x40? I've seen someone who looks new (or at least someone I've never seen before, someone with a low post count), and (s)he has a larger avatar. EDIT: I just checked in the control panel, and there appear to be no changes here.
Is your avatar still animated or is this an illusion? Please Register or Log in to view the hidden image! Oddly. I'll check that. Actually, it should be 60x60 by default.