Remember, the pin does not take the strings tension, or really even hold the string in at all. What the pin does is push the ball end over (toward the neck) so it can lock up against the underside of the bridge (bridge plate). The pins should never need to be pushed in hard at all. Make sure the ball end is not stuck on the bottom of the pin, but instead in front of the pin, towards the neck. Here are some tips from Frank Ford at frets.com
http://www.frets.com/FRETSPages/Musi...tringing1.html