Error Code 10061: Connection refused

I am trying to access a set of servers configured to be load-balanced by F5 through an ISA proxy. I get this error message from the proxy each time I try to access it:

Error Code 10061: Connection refused Background:The server you are attempting to access has refused the connection with the gateway. This usually results from trying to connect to a service that is inactive on the server.

Please, how can I resolve this problem?

Thank you in advance