if its due to bass, then live with it, once you get rid of that rattle, another will come. Only solution is alot of sound deadening to bulk up the panels. Even high build quality cars such as veedubs eventually loosen and begin to rattle after months of heavy bass.
if you really want to stop the rattling though, take them off, get the sticky double sided tape which youd put license plates on with, and put that behind it, should be enough to stop it rattling, and it will come off if you really want it off later.
[Edited by Friction on 14 November 2004 at 10:47pm]