UPDATE:  That was the problem.  I'm shocked I didn't catch it at first, because you can clearly see it in the picture I uploaded.

I followed the setup directions to the word, removing all tape and all three plastic retainers. Upon turning it on, the head moves to the right, and once it hits the sensor to the right, the back/forward motor tries moving but it just grinds.  Looking at the belt, you can see some vibration like the teeth are slipping. It moves very little towards the back.  I tried moving it back/forward by hand and there is an ungodly amount of resistance. 

One thing I did notice is that the left-hand belt is threaded through in almost a figure-eight, instead of a regular oval loop.  Is this normal?

Thanks in advance!