Quite late, but yes, I confirm with GateIn 3.2.0-GA : when trying to access to the portal page, with some Gadgets in it, and with a GadgetServer that is not on the same server as the GateIn server, then I get the same kind of error.
The error is comes from a connection problem, when trying to retrieve the Metadata of the Gadget, from the GadgetServer,... en ends with strange message of "Method not found" for the gadget JSON, or error when trying to render the gadget, etc...
The error from the real cause (retrieve the Metadata of the Gadget) shall be thrown (or indicated with a big warn) with a better way.
This seems to be on the way to be solved : see :
Bug 824860 - Error while rendering doodle gadget when source is dead
Services management and Site Export/Import don't start