If so, then just open your DS, remove the buttons and clean it with Q-tips and rubbing alcohol.
If you have a DS Lite just accidentally spill a small amount of rubbing alcohol on the lid of the DS.
I did that with mine and isopropyl alcohol was literally coming out of every crack of the DS. Somehow it even got in the battery compartment, literally coating everything but the positive and negative contacts (and definitely voiding the warranty that I probably haven't had in a while since the moisture indicator got pwned). How the hell is that even possible? :|
In its defense, after popping out the battery and wiping the entire unit down (including the insides of both cartridge ports and the stylus holder, which were all soaked for some reason) it worked without a problem (it's been about two weeks since that happened, too, so it's definitely fine). Cheaply made? Definitely. Reliable and durable? No doubt.