Why does satellite certificate activation fail with "Unhandled exception: unsupported version: -1" ?

Issue

• trying to activate Satellite server to Red Hat Network

• error when running rhn-satellite-activate:

  # rhn-satellite-activate -vvv --rhn-cert=<path to cert>
  RHN_PARENT: satellite.rhn.redhat.com 
  HTTP_PROXY: <proxy hostname>:<port>
  HTTP_PROXY_USERNAME: <username> 
  HTTP_PROXY_PASSWORD: <password> 
  CA_CERT: /usr/share/rhn/RHNS-CA-CERT 
  Checking
  cert XML sanity and GPG signature: '/usr/bin/validate-sat-cert.pl
  --keyring /etc/webapp-keyring.gpg
  /etc/sysconfig/rhn/rhn-entitlement-cert.xml-25157-1265298973.70446110' 
  Database connectioned initialized: refer to default_db setting in /etc/rhn/rhn.conf 
  Attempting local RHN Certificate push (and therefore activation) 
  Executing: remote XMLRPC deactivation (if necessary). 
  Executing: remote XMLRPC activation call. 
  Error reported from RHN: <Fault -2: 'unhandled internal exception: unsupported version: -1'> 
  ERROR: unhandled XMLRPC fault upon remote activation: <Fault -2: 'unhandled internal exception: unsupported version: -1'> 
  
  ERROR: <Fault -2: 'unhandled internal exception: unsupported version: -1'>