I would pull shorter putts left all too regularly as well. I always have to watch ball position like scotts33 says and that I have the putter head level. If its a right to left breaking putt I will even get the head more toe down ala Stricker as that seems to help me hit my line.
Some of it is just my stroke. I tend to start the putter a bit outside and then arc it back inside. So on shorter putts I tend pull it left and on longer ones I will push it right. I find practicing pushing balls to the hole helps straighten me out and smooths out my stroke.