Zenoss crashing

We have had a Zenoss installation for a couple of years. Everything was fine until about a several weeks ago when the system being out of memory. There was no significant event that could've led to that. We rebooted the server, and in a week it hang again. We rebooted, stopped the service cleanly and cleared and recreated the session table. In a few days it hang again. We upgraded to 4.2.5 (it was 4.2.0), the upgrade seemed to have gone clean and neat. The system hang out of memory again five days later, and after a reboot once again two days later.

Sometimes Zenoss website stops responding. Sometimes it crashes out with some kind of a dump.
In any way once the Zenoss is broken I cannot ssh into the server nor log into shell via console - I get out of memory error message. I cannot even do a Ctrl-Alt-Del to the server and have to power cycle it.

How can we cure this symptom

System information:

[zenoss@zenoss02 ~]$ uname -a
Linux zenoss02 2.6.32-279.el6.x86_64 #1 SMP Fri Jun 22 12:19:21 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

[zenoss@zenoss02 ~]$ cat /etc/issue
CentOS release 6.3 (Final)
Kernel \r on an \m

[zenoss@zenoss02 ~]$ rpm -qa |grep -i mysql
MySQL-shared-5.5.39-2.linux2.6.x86_64
MySQL-client-5.5.39-2.linux2.6.x86_64
MySQL-server-5.5.39-2.linux2.6.x86_64
MySQL-shared-compat-5.5.39-2.linux2.6.x86_64

[zenoss@zenoss02 ~]$ rpm -qa |grep -i zenoss
zenossdeps-4.2.x-1.el6.noarch
zenoss-4.2.5-2108.el6.x86_64

[zenoss@zenoss02 ~]$ zenoss xstatus
Status | PID | Daemon
-------------------------------------------------------------------
Running 4531 zeneventserver
Running 4743 zopectl
Running 4748 zenrrdcached
Running 4803 zenhub
Running 4847 zenjobs
Running 4916 zeneventd
Stopped zenping
Running 5110 zensyslog
Running 5094 zenstatus
Running 5129 zenactiond
Running 5434 zentrap
Running 5239 zenmodeler
Running 5287 zenperfsnmp
Running 4078 zencommand
Running 4131 zenprocess
Running 4134 zredis
Running 4177 zenwin
Running 4232 zenwinperf
Running 4276 zeneventlog
Running 4311 zenpython
Running 4346 zenjmx

zenping crashed out on startup:
Daemon: zenping starting...
Traceback (most recent call last):
File "/opt/zenoss/Products/ZenStatus/zenping.py", line 76, in
zcml.load_site()
File "/opt/zenoss/lib/python/Zope2/App/zcml.py", line 46, in load_site
_context = xmlconfig.file(site_zcml)
File "/opt/zenoss/lib/python/zope/configuration/xmlconfig.py", line 646, in file
include(context, name, package)
File "/opt/zenoss/lib/python/zope/configuration/xmlconfig.py", line 548, in include
processxmlfile(f, context)
File "/opt/zenoss/lib/python/zope/configuration/xmlconfig.py", line 380, in processxmlfile
parser.parse(src)
File "/opt/zenoss/lib/python/_xmlplus/sax/expatreader.py", line 109, in parse
xmlreader.IncrementalParser.parse(self, source)
File "/opt/zenoss/lib/python/_xmlplus/sax/xmlreader.py", line 123, in parse
self.feed(buffer)
File "/opt/zenoss/lib/python/_xmlplus/sax/expatreader.py", line 216, in feed
self._parser.Parse(data, isFinal)
File "/opt/zenoss/lib/python/_xmlplus/sax/expatreader.py", line 364, in end_element_ns
self._cont_handler.endElementNS(pair, None)
File "/opt/zenoss/lib/python/zope/configuration/xmlconfig.py", line 359, in endElementNS
self.context.end()
File "/opt/zenoss/lib/python/zope/configuration/config.py", line 620, in end
self.stack.pop().finish()
File "/opt/zenoss/lib/python/zope/configuration/config.py", line 774, in finish
actions = self.handler(context, **args)
File "/opt/zenoss/lib/python/OFS/metaconfigure.py", line 46, in loadProducts
xmlconfig.include(_context, zcml, package=product)
File "/opt/zenoss/lib/python/zope/configuration/xmlconfig.py", line 548, in include
processxmlfile(f, context)
File "/opt/zenoss/lib/python/zope/configuration/xmlconfig.py", line 380, in processxmlfile
parser.parse(src)
File "/opt/zenoss/lib/python/_xmlplus/sax/expatreader.py", line 109, in parse
xmlreader.IncrementalParser.parse(self, source)
File "/opt/zenoss/lib/python/_xmlplus/sax/xmlreader.py", line 123, in parse
self.feed(buffer)
File "/opt/zenoss/lib/python/_xmlplus/sax/expatreader.py", line 216, in feed
self._parser.Parse(data, isFinal)
File "/opt/zenoss/lib/python/_xmlplus/sax/expatreader.py", line 353, in start_element_ns
AttributesNSImpl(newattrs, qnames))
File "/opt/zenoss/lib/python/zope/configuration/xmlconfig.py", line 232, in startElementNS
self.context.begin(name, data, info)
File "/opt/zenoss/lib/python/zope/configuration/config.py", line 617, in begin
self.stack.append(self.stack[-1].contained(__name, __data, __info))
File "/opt/zenoss/lib/python/zope/configuration/config.py", line 969, in contained
return RootStackItem.contained(self, name, data, info)
File "/opt/zenoss/lib/python/zope/configuration/config.py", line 794, in contained
factory = self.context.factory(self.context, name)
File "/opt/zenoss/lib/python/zope/configuration/config.py", line 556, in factory
raise ConfigurationError("Unknown directive", ns, n)
zope.configuration.xmlconfig.ZopeXMLConfigurationError: File "/opt/zenoss/etc/site.zcml", line 16.2-16.23
ZopeXMLConfigurationError: File "/opt/zenoss/ZenPacks/ZenPacks.zenoss.CalculatedPerformance-2.0.0.egg/ZenPacks/zenoss/CalculatedPerformance/configure.zcml", line 41.4
ConfigurationError: ('Unknown directive', u'http://namespaces.zope.org/browser', u'directRouter')