  We perform a two-flavor dynamical lattice computation of the Isgur-Wise
functions tau_{1/2} and tau_{3/2} at zero recoil in the static limit. We find
tau_{1/2}(1) = 0.297(26) and tau_{3/2}(1) = 0.528(23) fulfilling Uraltsev's sum
rule by around 80%. We also comment on a persistent conflict between theory and
experiment regarding semileptonic decays of B mesons into orbitally excited P
wave D mesons, the so-called "1/2 versus 3/2 puzzle", and we discuss the
relevance of lattice results in this context.
