Contact Form Problem – Internal Server Error

I recently installed prophoto4, and i also purchased a new template.

I set everything up yesterday, but the contact form is not working.

The contact form loads (but only with simple mode)

When i test out the contact form, and click submit, i get this error:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Can anyone please help me?

Thank you!