Code:
500 Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
This can be caused by this entry in .htaccess in the root html folder:

Code:
php_flag register_globals Off
comment out this line by adding a # to the line, like below

Code:
#php_flag register_globals Off
You should double check to make sure register_globals is off.

You can do this by making a phpinfo.php file, uploading it, and calling it from your web browser.

Name this phpinfo.php

Code:
<?php
phpinfo();
?>
Upload it to your public_html directory

Call it in your web browser

http://www.yoursitename.com/phpinfo.php

Make sure this line has the Off Off values:

Code:
register_globals	Off	Off
If not, you need to disable register_globals - see this post:
How To Turn Off Register Globals

When all is OK with register_globals - delete the phpinfo.php file from your server. It is not safe to leave it there as it contains much information about your server configuration.

Smoge