Canon Rebel XS - Horizontal lines

[Gadgetx23]

Does anyone have an idea of what could be causing this? It happens randomly; sometimes 1 in 10 photos; sometimes 1 in 100.

These samples are cropped. The problem usually extends horizontally through the entire image.

These were not shot RAW, jpg only. I've use 2 different memory cards, same problem.

 

[KmH]

Does anyone have an idea of what could be causing this? It happens randomly; sometimes 1 in 10 photos; sometimes 1 in 100.

These samples are cropped. The problem usually extends horizontally through the entire image.

These were not shot RAW, jpg only. I've use 2 different memory cards, same problem.

JPEG converts images into 8 pixel by 8 pixel squares. The arrow in the lower left corner of the above image is pointing to a stack of 8x8 pixel squares.

You can check out more info about JPEG at http://en.wikipedia.org/wiki/JPEG

I wonder what image size you have selected for your XS to capture? Fine? Medium? Small?