try this: place a small strip of cloth or sponge between the bridge and the guitar (only a little so it doesnt show) then turn the screws that hold the spring claw 1/2 turn clockwise. that should stop the rattle. Putting blocks in stops all tremolo activity and can be a bit dangerous. you could also loosen the strings, get a pencil and rub the under side of the strings where they would slot into the nut. this lubricates them and stops them sticking when you bend the strings or use the trem (not that you should really use the bar for more than simple vibrato on a strat) :)