Why does rhn-satellite-activate, satellite-sync, or yum update (via RHN Proxy) against RHN Classic fail with error "IOError: CRC check failed" ?

Issue

• Satellite server sometimes returns the error below when trying to activate a new Satellite Certificate (rhn-satellite-activate) or synchronize content (satellite-sync)
• "yum update" on Red Hat Enterprise Linux against RHN Proxy (that is connected to RHN Classic as upstream server) sometimes fails with error below

• error traceback:

  Exception Handler Information
  Traceback (most recent call last):
    File "/usr/share/rhn/satellite_tools/xmlSource.py", line 132, in process
      self.__parser.parse(self.__stream)
    File "/usr/lib/python2.4/site-packages/_xmlplus/sax/expatreader.py", line 109, in parse
      xmlreader.IncrementalParser.parse(self, source)
    File "/usr/lib/python2.4/site-packages/_xmlplus/sax/xmlreader.py", line 124, in parse
      buffer = file.read(self._bufsize)
    File "/usr/lib/python2.4/site-packages/rhn/transports.py", line 797, in read
      return self.file_obj.read(amt)
    File "/usr/lib/python2.4/gzip.py", line 225, in read
      self._read(readsize)
    File "/usr/lib/python2.4/site-packages/gzipstream.py", line 168, in _read
      self._read_eof()
    File "/usr/lib/python2.4/site-packages/gzipstream.py", line 208, in _read_eof
      self._gzip.GzipFile._read_eof(self)
    File "/usr/lib/python2.4/gzip.py", line 309, in _read_eof
      raise IOError, "CRC check failed"
  IOError: CRC check failed