Won't write to SD Card

My T1i powers on fine but when I try and take a picture, the red busy light stays on for a while but nothing gets written to the SD card. I’ve tried a brand new card and a low level format of the new card with no luck. I’ve also reset the camera to defaults - again, no luck. Also, the screen will intermittently get vertical lines across it after taking a picture (when trying to write to the card). Anyone know what causes these symptoms and how to fix?