Hi,
Well no response and I trawled the source code and can only find an undocumented reference to a WICED code 26 meaning INVALID_SOCKET.
Anyway - I resolved the problem by reviewing my code.
Since going into Manual mode (due to other issues) I had not checked if ALL my network dependent code was run AFTER connecting to the cloud etc.
So I had one Init function which called begin on my UDP :-O. When I moved that code to AFTER cloud connection - my UDP is working again ;-).
Hope this might help someone else…
Graham