I had that problem once when I blead the brakes. What little was left in the bleeder itself sort of leaked out and onto the threads. It looked like it was leaking (a little goes a long way) but after I sprayed the area down with brake cleaner it was fine. You want them tight but not too tight. SpeedBleeders have some goop on the threads that makes turning them a little harder than the normal bleeder. I don't torque mind down I just make them nice and snug. I thought they were a little longer than stock too, maybe it's to make up for the check valve in there.