Highend WP Theme Installed – 500 Internal Service Error

Hello:

I installed the theme today, added the recommended plugins, and now I cannot access a single page on my WordPress site. Every page returns the following:

Internal Server Error

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

Please contact the server administrator, 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.

I do not understand, apparently the URLs were changed for the admin. I cannot even access the dashboard, same error.