Same problem
I've noticed it since upgrading my 2011 15" MBP. It seems way more prominent in Apple applications like preview, itunes, etc, but that could just be me.
I don't think it's the Chrome Helper thing (which I also had, but has since been addressed in an update), although theres a whole thread on that over at the google forums.
Not sure what it is, but it's annoying as all hell.