Problem
After installing a SSL certificate, the following error appears when connecting to the server using Firefox:
Secure Connection Failed
"An error occurred during a connection to <server-name>.
SSL received a record that exceeded the maximum permissible length.
(Error code: ssl_error_rx_record_too_long)"
Cause
The web server is sending non-secure (HTTP) data where secure (HTTPS) data is expected by Firefox. This can be confirmed by going to http://server-name:443 instead of https://server-name.
Resolution
Check the configuration of the server to ensure that SSL has been configured correctly. This most commonly occurs when using Apache or Tomcat as the web server, though it can certainly occur in other server types.
Points to consider when troubleshooting this error in either Apache or Tomcat:
In Apache, check that the Listen <port> directive matches the port number in the VirtualHost directive for the website being secured, and that the SSL configuration statements (SSLEngine On, SSLCertificateFile <filename> and so on) appear in the VirtualHost directive for the website or in the SSL configuration file for the server.
In Tomcat, check that the connector in server.xml is configured to use SSL (there should be scheme="https" secure="true", as well as keystoreFile and keystorePass statements) and that the port number listed in the connector is what is expected -- if using the default port (8443), it needs to be specified as part of the URL or be appropriately redirected on the server. Tomcat may also be switching to non-secure mode for a connector where the keystore is corrupt; try creating a new keystore and replacing the SSL certificate.
More info here