Vertical/Horizontal lines through images

Hi,I am currently a photography student in Boston, and having some serious issues with my images. I recently sent my camera back to Canon, as it was still under warranty. I thought everything was ok, but after shooting the last few days and uploading my images, they are ALL coming out with vertical and horizontal lines through my images....red and blue dots all over them as well. Same thing that was happening before I sent it to Canon. Anyway, it doesn't matter whether I am shooting at a 100 iso, or larger. It still does this. I also thought maybe I was using bad CF cards, but recently started using a more prof. udma card. This did not fix anything either. I know the rest of gear is fine, and finding this is definitely a camera issue. I at first, thought it was the program I am using to view the files (through bridge and Lightroom) but tried viewing in another program, and they still look the same. I don't even know what to do, and am grasping at any assistance I can get. I need to figure this out asap, as I have classes every day, and can't get my assignments done! Please help!