Free Spirit Treadmill E1?

My treadmill turns on, there is a display but the belt won't move. As soon as you increase the speed to 0.5 it beeps and E1 comes up on the screen. I have checked some of the other posts online, and read that it could be a dirty optical sensor. We opened it up and vacuumed out all the crap, but still no luck.

This unit is about 6 years old, receives regular use, manufactured by Horizon. Any suggestions for home repair? Do I bother calling Sears in for service or get a new unit?