  Spin dependent transport in a ferromagnet/superconductor/ferromagnet single
electron transistor is studied theoretically with spin accumulation, spin
relaxation, gap suppression, and charging effects taken into account. A strong
dependence of the gap on the magnetic state of the outer electrodes is found,
which gives rise to a negative magneto-resistance of up to 100 %. We predict
that fluctuations of the spin accumulation due to tunneling of quasi-particles
can play such an important role as to cause the island to fluctuate between the
superconducting
