you have a .htaccess file in your store or public folder?. make a backup of it , then remove for a test
if this file contains
instructions which the web server doesn't know how to parse, then it will generate this error message

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.

Apache/1.3.33 Server at clubina.com Port 80