Mine started doing that about 4 years ago, and cleaning helped at first, but it became a progressively terminal issue. I was intimidated by replacing the unit with an aftermarket at first, but it's really not that bad if you're mechanically inclined. I simply purchased an inexpensive cd player, and spent some extra on replacing the stock speakers (highly reccomended). I'm not ashamed to say that I bought my stuff from Crutchfield. I probably could have gotten a better value, but I valued the simplicity of having predetermined kits available for easy retrofitting. The wiring diagrams just take some patience to sort out, but otherwise it's pretty straightforward. I spent less than $200 and it sounds better than the stock unit did.
