eventd exception: failed to process event

I have serious problem with zenoss 4.2.3 - i have noticed that some events are not appearing in eventconsole. Then i checked eventd.log and spotted many such messages:

2013-05-28 12:18:15,747 INFO zen.eventd: Failed to process event, forward original raw event: {'uuid': u'e8e58fa8-c77f-11e2-bb47-000c2940a3b9', 'first_seen_time': 1369736293122L, 'monitor': u'localhost', 'actor': {'element_identifier': u'77.242.226.2', 'element_sub_type_id': 2, 'element_uuid': u'a64fcca6-ae99-42e9-8ac5-e2dd357361ad', 'element_type_id': 1, 'element_sub_identifier': u'dev_md6, mounted on_ _packages_mnt_jpfe-common-11.4R3.7'}, 'summary': u'threshold of high disk usage exceeded: current value 22920.000000', 'agent': u'zenperfsnmp', 'created_time': 1369736293122L, 'details': [{'name': u'max', 'value': [u'20628.0']}, {'name': u'current', 'value': [u'22920.0']}, {'name': u'how', 'value': [u'exceeded']}, {'name': u'manager', 'value': [u'localhost.localdomain']}], 'message': u'threshold of high disk usage exceeded: current value 22920.000000', 'event_key': u'usedBlocks_usedBlocks|high disk usage', 'event_class': u'/Perf/Filesystem', 'severity': 3}

2013-05-28 12:18:15,747 ERROR zen.eventd:

Traceback (most recent call last):

  File "/opt/zenoss/Products/ZenEvents/zeneventd.py", line 107, in processMessage

    eventContext = pipe(eventContext)

  File "/opt/zenoss/Products/ZenEvents/events2/processing.py", line 429, in __call__

    plugin.resolveIdentifiers(eventContext, self._manager)

  File "/opt/zenoss/Products/ZenEvents/events2/processing.py", line 408, in resolveIdentifiers

    EventField.Actor.ELEMENT_SUB_UUID

  File "/opt/zenoss/Products/ZenEvents/events2/processing.py", line 363, in _resolveElement

    identifier)

  File "/opt/zenoss/Products/ZenUtils/FunctionCache.py", line 69, in wrapped_f

    value = f(*args, **kwargs)

  File "/opt/zenoss/Products/ZenEvents/events2/processing.py", line 136, in getElementUuidById

    return self.uuidFromBrain(results.results.next())

StopIteration

I have tried to fix db according to http://wiki.zenoss.org/Fixing_ZODB_Integrity_Issues

but with no luck.