C.K. Sample

Anybody else having this problem? I thought the internal mic in my 1st gen. 12-inch had failed and was planning on sending my machine off for repair as soon as I can stand to part with it. Anyway, yesterday I am using an air can to clean out anything that might have been mucked up in my keyboard, and I decide what the heck and give the mic a spray of air, in case it was just dirty. Anyway, to my surprise the mic actually registered some response for a change, but still not any sort of steady stream of noise or anything useful. Then all of a sudden this morning I noticed a sort of white noise coming from my speakers, and it became quickly evident that slight noises were being picked up by my mic and played through the speakers! I had to change the system preferences for sound input to line-in to get the noise to stop, but how can this happen? Is this a hardware / software issue or a combination of both? I just tried switching back over to mic again and now it is acting like it is non-functional again. A short perhaps? grrr…