That link you've posted returns a 500 Internal Error. Your host should see this in his log I would think.
http://www.checkupdown.com/status/E500.html
Ask your host if they're using SuPHP and if so, be sure all
files that do not work like this, have permissions of
644 and
folders 755
You might also go to your vbadmin page > Maintenence section > Diagnostics > Suspect File Versions tool and use it to check your vb files for issues.