Same here... 2001 RX300
Was lovely and quiet, now, after have new (genuine) discs and pads fitted all round, the front rattles on pot holes, speed bumps and the like, I just can't seem to find out where it's coming from as everything seems "tight" and solid when I look at it (the rattle sounds like something is really loose :-/ ) ..... it wouldn't be too bad I suppose, but it's embarrasing when pedestrians look round (or jump out the way in one case!!) when you drive past :-(