[RHN Proxy 5.4] Why does rhncfg-client and rhncfg-manager return 400 "Bad Request" or 500 "Internal Server Errors" when working with config files?

[root]# rhncfg-manager list
XML-RPC call error: <ProtocolError for test.com /CONFIG-MANAGEMENT: 500 Internal Server Error>
[root]# rhncfg-client list
XML-RPC call error: <ProtocolError for test.com /CONFIG-MANAGEMENT: 500 Internal Server Error>
[root]# rhncfg-client diff
XML-RPC call error: <ProtocolError for test.com /CONFIG-MANAGEMENT: 500 Internal Server Error>
[root]# rhncfg-client get 
XML-RPC call error: <ProtocolError for test.com /CONFIG-MANAGEMENT: 500 Internal Server Error>
[root]# rhncfg-client channels
XML-RPC call error: <ProtocolError for test.com /CONFIG-MANAGEMENT: 500 Internal Server Error>

[root]# rhncfg-client list
XML-RPC call error: <ProtocolError for test.com /CONFIG-MANAGEMENT: 400 Bad Request>

[Thu Nov 11 11:04:15 2010] [error] PythonHandler server.apacheServer::Handler:
Traceback (most recent call last):
[Thu Nov 11 11:04:15 2010] [error] PythonHandler server.apacheServer::Handler: 
 File "/usr/lib64/python2.4/site-packages/mod_python/apache.py", line 299, in
HandlerDispatch\n    result = object(req)
[Thu Nov 11 11:04:15 2010] [error] PythonHandler server.apacheServer::Handler: 
 File "/usr/share/rhn/server/apacheHandler.py", line 210, in handler\n    ret =
self._req_processor.process()
[Thu Nov 11 11:04:15 2010] [error] PythonHandler server.apacheServer::Handler: 
 File "/usr/share/rhn/server/apacheRequest.py", line 465, in process\n   
params, method = self.decode(_body)
[Thu Nov 11 11:04:15 2010] [error] PythonHandler server.apacheServer::Handler: 
 File "/usr/share/rhn/server/apacheRequest.py", line 389, in decode\n   
self.parser.feed(data)
[Thu Nov 11 11:04:15 2010] [error] PythonHandler server.apacheServer::Handler: 
 File "/usr/lib64/python2.4/xmlrpclib.py", line 527, in feed\n   
self._parser.Parse(data, 0)
[Thu Nov 11 11:04:15 2010] [error] PythonHandler server.apacheServer::Handler:
ExpatError: not well-formed (invalid token): line 1, column 0