Haven't fully debugged yet, but it seems large messages with long strings being sent from a client to a server do not work. In this case, I'm working with a large serialized json object that I need to pass to a server.
Could it be something along these lines:
http://stackoverflow.com/questions/1639312/avoiding-localconnections-40k-size-limit-when-data-object-may-be-larger-than-40