It is not a configuration problem. You are certainly using the latest BFGminer version which has broken its JSON-RPC protocol implementation (string IDs are not allowed in JSON-RPC).
Quote
id - The request id. This can be of any type. It is used to match the response with the request that it is replying to.
http://json-rpc.org/wiki/specification
http://json-rpc.org/wiki/specification
(To be fair that is probably quite the nuisance to implement correctly...)