If you talk directly to bitcoin via JSON-RPC calls, you might need to change your code to recognize the new HTTP status codes and the new format for the 'error' member of the JSON response. For example:
BEFORE, send {"id":"123", "method": "nosuchmethod", "params": [] } , get response:
Code:
HTTP/1.1 500 Internal Server Error
...
{"result":null,"error":"Method not found.","id":"123"}
AFTER:
...
{"result":null,"error":"Method not found.","id":"123"}
Code:
HTTP/1.1 404
...
{"result":null,"error":{"code":-32601,"message":"Method not found"},"id":"123"}
...
{"result":null,"error":{"code":-32601,"message":"Method not found"},"id":"123"}
I also removed the broken 'Batch' support, to simplify the code. I had JSON-RPC-2.0 batch support working properly, but backed those changes out because JSON-RPC 2.0 is way too cutting-edge for bitcoin to support right now (none of the JSON-RPC glue libraries support it yet, and the spec is still changing a bit).