new virtual sites installing scripts results in server 500 errors

Creating a new virtual site works fine but trying to install a script results in a server 500 error. Installing a script to an existing site works fine.

virtualmin log for the virtual site:

[Thu Oct 29 15:27:41 2009] [warn] (104)Connection reset by peer: mod_fcgid: read data from fastcgi server error.
[Thu Oct 29 15:27:41 2009] [error] [client] Premature end of script headers: install.php
[Thu Oct 29 15:30:02 2009] [error] [client] Directory index forbidden by Options directive: /home/brian/public_html/