Hi Bob,
it seems you haven't received my private mail. I report it here:
Your htaccess.txt is the Joomla's default one, so now you should have a ".htaccess" file on your web root folder. It's strange you get a 403 error instead of a 404. You should check your virtual host settings, but I don't know if you have access to this. So, as fast workaround, try to add this lines to the end of .htaccess:
ErrorDocument 404 /
ErrorDocument 403 /
In this way you are telling to Apache to let manage to Joomla all the errors 403 and 404, but AllowOverrides must be enables for these.
Let me know,
Luigi
P.S. If you want, I can send you the modified .htaccess file, so you just need to copy it on the web root folder.