The easiest way for me is to pull the center up but just slightly, just enough to disengage and then pry up the outer portion, if you pull the center up too far it spreads the outer portion again which is why it is so hard to pullt it out. Did that make sense? easier to show.
+1.. I learned the hard way. I've got a bag full of extra now. haha
just as wes stated.. pull it up a hair, then push the center in. Make sure you curse at it a little bit on each one. :biggrin: