You might check your power cord connection and your input line from scanner to computer to see if both are firmly connected, no loose wires or that sort of thing. However, if the artifacts are showing up in the same place with each scan and the noise is consistant as well, the ccd components are probably close to being shot. There is a technique known as darkfield subtraction which will remove noise but I dont think it can be done with a flatbed scanner, and it is a bit of a pain. Briefly it consists of taking a scan/photo with no light getting to the ccd for the same amount of time your scan/photo will take. The only thing which will show on the first scan is a photo which looks like a snowstorm. This is subtracted from the actual photo/scan. The noise is cancelled out, leaving the "clean" photo. Not difficult with a ccd camera, but for a scanner..... You might also try using the blending options routine in
PS, it might be possible to simulate a darkfield subtraction with it. I kinda think the new scanner route is the best, if the finances permit. Good luck, Tom