How to fix an i-run treadmill?

I was running 6 mph on my treadmill and all of a sudden it stopped. When I got off the treadmill it started working again, but as soon as I stepped on it. It stopped. I am not a large person so it can't be my weight (i hope)

The belt is going round but it appears to be having some trouble. Can anyone give me some advice on how I can fix this? I'm lost without my treadmill.