any suggestions?

what's the best way to clean/fix a scratched or smudged dvd? my season 2 disc two of the simpsons appears to have something wrong with it as the end of "Itchy and Scratchy and Marge" and the beginning of "Bart Gets Hit By a Car" are messed up. They pixelate although the disc doesn't stop completely. Any suggestions as to what I should do? (note: i have tried wiping it with a lens cloth). Are there any effective dvd cleaner kits out there?