till now i never needed to clean a sensor. i'm fairly careful, and dust usually comes off in the cleaning cycle. but i recently bought a used G3 from a reputable dealer, and it arrived with 2 large scratches over the sensor that luckily don't affect the pics at all. it also has a fat piece of gunk (edited from dust) that won't shake off, so i took the camera to samy's for a sensor cleaning - they declined, saying they won't clean a sensor with such large scratches on it. the local camera repair store might do it for a much higher price, but they're not sure they're willing to do it, and would have to take several days to decide. we've just took a closer look, and the stuff on the sensor isn't dust - it's some kind of gunk that's stuck on there pretty well. since the camera was so cheap, i'm thinking of cleaning the sensor myself, but i'm concerned that using the wrong liquid might stick in the scratches, making the scratches appear in the photos. any suggestions on what i can use? i'm past the return time for the camera, but i do have a warranty that is still in effect. thanks!