The most common cause of server 500 errors deal with .htaccess file.
We run SuPHP which protects you against php injection attacks. If you have not been on a server with SuPHP you need to be careful about you .htaccess entries.
You cannot directly add php values to your .htaccess file, the must be added to a file called php.ini that will reside in whatever directory you need to apply the changes. This file works like a .htaccess files in the scheme of if this file exists in your /public_html folder it affects all subdirectories.
If you are going to use a custom php.ini we recommend that you place the following in your .htaccess file:
deny from all
Then in your php.ini file you need to list the commands just as if they were in the server's php.ini file; example, the old way of changing register global in the .htaccess file you would enter php_value register globals on but in the php.ini file it should say register_globals = On.
Some other examples are php_value magic_quotes_gpc 0 in the .htaccess file should be magic_quotes_gpc = On in the php.ini file. To figure out what it should read simple look at our phpinfo gile located at http://www.okie.net/phpinfo