Problems with my Trackpad

I just bought a 2011 model 11" Air and it has been flawless. I am coming from a MBP 15" also 2011 model.

The Trackpad is somehow different than the external one I was mostly using for my 15" MBP.

When I attempt to scroll with two fingers it sometimes doesn't seem to recognize that and will do the zoom in or zoom out function. This is especially bad in preview when working on pdf files.

My question: Is this a macbookAir problem, I mean hardware wise,

or is it because the 11" Trackpad is smaller than my external one and I have too big fingers for this one?

thanks for the input!


Edit: maybe some of you could try this out: When you place one finger on the Trackpad of the Air, watch the mouse. Does it move, from left to right? (Just a couple mm, but it could be the movement that is causing my problems....