log in and checkout not working

I have a new site programmed, but am having issues. https://www.bmoreorganic.com Zen version 1.3.0

Site works fine unless you either try to log on, or you try to check out. Then I get a file not found message.

estimate shipping module does work......

Hosted by sashbox, but for weeks they have not answered or returned phone calls or emails.

log error message is:
[Fri Mar 13 19:24:57 2009] [error] [client 96.234.253.85] File does not exist: /home/bsminc1/bmoreorganic.com/403.shtml

[Fri Mar 13 19:24:57 2009] [error] [client 96.234.253.85] client denied by server configuration: /home/bsminc1/bmoreorganic.com/includes/templates/arch_shoppe/images/index.php

[Fri Mar 13 19:24:57 2009] [error] [client 96.234.253.85] client denied by server configuration: /home/bsminc1/bmoreorganic.com/includes/templates/arch_shoppe/images/index.php