I agree, maybe try a different brand of fluoro. When I first started using fluoro leaders I was using 17# Berkley Vanish (w/ 30# braid mainline) and had problems with the leader breaking on the hookset. Since then I've used 3 different brands of Seaguar (Red Label, Abrazx, Invizx) and haven't broken a leader since then. I've always used a uni-to-uni knot with more wraps on the braid and less on the fluoro to get the knots about the same size. A Trilene knot for attaching fluoro to the bait or hook.