Well Pierre, I wish I had a simple answer for you. I own a Plustek brand flatbed scanner which I really like better than my newer all-in-one Hewlett Packard. The Plustek I purchased in 2002 in Taif Saudi Arabia. After 7 years it still works great, has scanned literally thousands of images with no problem. I bought this model mainly because it will also scan slides and negatives. When I scan the transparent films I get the same annoying type strip on the image. Fortunately it's only one strip, very narrow (light blue color) and it (like yours) runs the length (longitudinal axis) of the picture. I've yet to find the solution to the problem. But if I do,,,I'll let you know. It must have something to do with the scanning process itself, as it appears common to different brands of scanners. Good Luck