It's a generic 500 error with no other information given. At this point I'm going to take a guess that there is something funky going on with how this particular host (JustHost) has things set up and I'm not clever (or currently able to spend time focusing close enough) to determine exactly what.
In the meantime I may try to get it up and running on one of the recommended free hosts just to get an idea of how it works.
Thanks for being responsive to my plight!