Problem
Why do I get omniORB.CORBA.BAD_PARAM: Minor: BAD_PARAM_WrongPythonType, COMPLETED_NO exceptions when invoking CORBA methods of components?
Solution
This occurs when you try to pass Python objects of the incorrect CORBA type to CORBA objects as in or inout parameters. omniORB does not provide any nice mechanism for determining precisely which parameter is bad so you'll have to look at them one at a time. The IDL->Python mapping document, http://www.omg.org/technology/documents/formal/python.htm, is a good starting point for figuring out which parameter is incorrect.
Of particular interest to developers is the fact that it's possible to create CORBA objects (an instance of an IDL struct for example) using the wrong Python object types. Then if you try to pass that CORBA-based object to some real CORBA method as an in or inout parameter it will fail with the exception indicated above! This can be very hard to debug.