RHN Satellite errors: <ProtocolError for satellite.rhn.redhat.com:443: 503 Service Unavailable>

Hello All,

Please forgive me if this has been covered before or if this is the wrong place; I'm new here, but I did search quite extensively on the portal and google before relenting and posting here.

While checking the daily sync logs this morning I discovered a new error with our RHN Satellite:

00:15:03 Red Hat Network Satellite - live synchronization
00:15:03    url: https://satellite.rhn.redhat.com
00:15:03    debug/output level: 1
00:16:03
00:16:03
ERROR: there was a problem synchronizing the information.
       Error message:
 

I logged into the satellite and am able to replicate this error line many times througout the running of satellite-sync, with the final debug traceback showing this:

9:52:49 ERROR: http error code :503; fault code: 0;
Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib64/python2.4/threading.py", line 442, in __bootstrap
    self.run()
  File "/usr/share/rhn/satellite_tools/satsync.py", line 2129, in run
    package_id, nvrea, self.sources)
  File "/usr/share/rhn/satellite_tools/satsync.py", line 2070, in _get_package_stream
    stream = rpmServer.getPackageStream(channel, nvrea)
  File "/usr/share/rhn/satellite_tools/xmlWireSource.py", line 480, in getPackageStream
    return self._rpc_call("getPackage", (channel, package_name))
  File "/usr/share/rhn/satellite_tools/xmlWireSource.py", line 447, in _rpc_call
    ret = apply(getattr(get_server_obj, function_name), params)
  File "/usr/lib/python2.4/site-packages/rhn/rpclib.py", line 678, in __call__
    result = self._send(self._name, args)
  File "/usr/lib/python2.4/site-packages/rhn/rpclib.py", line 387, in _request
    raise pe
ProtocolError:
 

This is a sudden development as our satellite server and network infra haven't changed a bit.  I thought it might have been an outage but cannot find anyone else talking about it, and can get as far as an HTTP 403 error when browsing manually to satellite.rhn.redhat.com:443, so the site appears to be fine.

Anyone have any advice on what else to check? 

Some details:  RHN Satellite version 5.4.1, embedded DB.

Thanks!