While starting `cobblerd` service on RHN Satellite v 5.4 server it fails with "ValueError: No JSON object could be decoded" error ?

Issue

• While starting cobblerd service on RHN Satellite server it fails with following error

# /etc/init.d/cobblerd start
Starting cobbler daemon: Traceback (most recent call last):
  File "/usr/bin/cobblerd", line 76, in main
    api = cobbler_api.BootAPI(is_cobblerd=True)
  File "/usr/lib/python2.6/site-packages/cobbler/api.py", line 128, in __init__
    self.deserialize()
  File "/usr/lib/python2.6/site-packages/cobbler/api.py", line 689, in deserialize
    return self._config.deserialize()
  File "/usr/lib/python2.6/site-packages/cobbler/config.py", line 208, in deserialize
    serializer.deserialize(self._profiles)
  File "/usr/lib/python2.6/site-packages/cobbler/serializer.py", line 122, in deserialize
    rc = storage_module.deserialize(obj,topological)
  File "/usr/lib/python2.6/site-packages/cobbler/modules/serializer_catalog.py", line 186, in deserialize
    datastruct = deserialize_raw(obj.collection_type())
  File "/usr/lib/python2.6/site-packages/cobbler/modules/serializer_catalog.py", line 156, in deserialize_raw
    datastruct = simplejson.loads(ydata, encoding='utf-8')
  File "/usr/lib64/python2.6/site-packages/simplejson/__init__.py", line 318, in loads
    return cls(encoding=encoding, **kw).decode(s)
  File "/usr/lib64/python2.6/site-packages/simplejson/decoder.py", line 335, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib64/python2.6/site-packages/simplejson/decoder.py", line 353, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded
                                                           [  OK  ]

• RHN Satellite server send traceback mails with following content , the /var/lib/rhn/tasko/sat/cobbler-sync-bunch/cobbler-sync_2159980_err file shows:

2012-08-09 10:38:00,564 [DefaultQuartzScheduler_Worker-4] ERROR com.redhat.rhn.taskomatic.task.CobblerSyncTask  - RuntimeExceptioneError trying to sync to cobbler: XmlRpcException calling cobbler.
java.lang.RuntimeException: XmlRpcException calling cobbler.
        at com.redhat.rhn.manager.kickstart.cobbler.CobblerXMLRPCHelper.invokeMethod(CobblerXMLRPCHelper.java:72)
        at com.redhat.rhn.taskomatic.task.CobblerSyncTask.execute(CobblerSyncTask.java:70)
        at com.redhat.rhn.taskomatic.task.RhnJavaJob.execute(RhnJavaJob.java:80)
        at com.redhat.rhn.taskomatic.TaskoJob.execute(TaskoJob.java:168)
        at org.quartz.core.JobRunShell.run(JobRunShell.java:216)
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:549)
Caused by:
redstone.xmlrpc.XmlRpcException: The response could not be parsed.
        at redstone.xmlrpc.XmlRpcClient.handleResponse(XmlRpcClient.java:434)
        at redstone.xmlrpc.XmlRpcClient.endCall(XmlRpcClient.java:376)
        at redstone.xmlrpc.XmlRpcClient.invoke(XmlRpcClient.java:165)
        at com.redhat.rhn.manager.kickstart.cobbler.CobblerXMLRPCHelper.invokeMethod(CobblerXMLRPCHelper.java:69)
        ... 5 more
Caused by:
java.io.IOException: Server returned HTTP response code: 503 for URL: http://server.example.com:80/cobbler_api
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1446)
        at redstone.xmlrpc.XmlRpcClient.handleResponse(XmlRpcClient.java:420)
        ... 8 more
2012-08-09 10:38:00,566 [DefaultQuartzScheduler_Worker-4] ERROR com.redhat.rhn.taskomatic.task.CobblerSyncTask  - re-throwing exception since we havent yet.
2012-08-09 10:38:00,567 [DefaultQuartzScheduler_Worker-4] ERROR com.redhat.rhn.taskomatic.task.CobblerSyncTask  - XmlRpcException calling cobbler.
2012-08-09 10:38:00,568 [DefaultQuartzScheduler_Worker-4] ERROR com.redhat.rhn.taskomatic.task.CobblerSyncTask  - redstone.xmlrpc.XmlRpcException: The response could not be parsed.