suphp is a apache setting , same as DSO and CGI
if you can choose betwean 2 versions of php then you are probaly running php as cgi but not sure about that ( i run only 1 version )
can you post a phpinfo page ?
Code:
<?php
phpinfo();
?>
on that way i can see the php version and php variables and maybe solve it from there
if that page also provide a 500 error then you definaly need to contact your host (unless you manage the server ) as there is a big php/apache error going on then
Greetings From PowerChaos