Although you have a comment regarding the importance of the slashes when defining your balancer, I found that your setup still did not work, however making the corrections to the slashes mentioned in this blog entry fixed my problems and made everything work well.

 http://www.kaigrabfelder.de/en/2008/10/21/proxy_no_protocol_handler_was_valid_for_the_url.html

 I hope it will helps others.

Thanks,

Sean