Solved
Just FYI -- I had the exact same problem. My MBP (2011 13'' i5) cursor would become erratic, right clicking, flicking between screens, and was often unresponsive to my actual input. It generally seemed that the trackpad was signaling inputs that weren't there, because when I would touch the trackpad with one finger it would respond as if I were using two, three or four.
I tried everything. I cleaned the trackpad, even removed it to ensure it wasn't sticking, all to no avail.
The only solution I found was to replace the trackpad. It's a super easy procedure and it's pretty cheap. I spent $40 (w/ shipping) for a trackpad and $2 for a tri-wing screwdriver.
So far, no erratic behavior. I think this is a problem with the MBP trackpads, since so many people have the same issue. Hopefully Apple recognizes the issue soon.