Hosts disconnect/reconnect in vCenter within a few seconds

I have 70 ESX hosts in vCenter on several different continents running ESX 3.0.1 to 4.1 with patches.  I reciently edited the vpxd.cfg file and added:

<heartbeat>
       <notRespondingTimeout>60</notRespondingTimeout>
</heartbeat>

I thought it would eliminate those false positives which also alert many people, some of whom get very worried when they see an alert like this.  How can I stop my hosts for causing this sort of quick disconnect / connect?  The change I made to vCenter doesn't seem to be working.  I'm seeing alerms over night that show a disconnect and a reconnect within the very same minute.  It happens to at least 3 hosts per day.  All of these false alarms are causing my department to ignore potentially valid alerts.  After I made the change to the cfg file restarted the entire server so I know it's in effect.

Heres the entire file... Let me know if there is a problem or what I can do.  Thanks!

<config>
  <level id="VmCheck">
    <logLevel>info</logLevel>
    <logName>VmCheck</logName>
  </level>
  <level id="CpuFeatures">
    <logLevel>info</logLevel>
    <logName>CpuFeatures</logName>
  </level>
  <log>
     <maxFileNum>10</maxFileNum>
     <level>info</level>
     <memoryLevel>verbose</memoryLevel>
     <compressOnRoll>true</compressOnRoll>
  </log>
  <alert>
    <log>
      <enabled>true</enabled>
    </log>
  </alert>
  <vmacore>
    <threadPool>
      <TaskMax>90</TaskMax>
    </threadPool>
    <ssl>
      <useCompression>true</useCompression>
    </ssl>
  </vmacore>
  <vpxd>
    <das>
      <serializeadds>true</serializeadds>
      <slotCpuMinMHz>256</slotCpuMinMHz>
      <slotMemMinMB>0</slotMemMinMB>
    </das>
    <filterOverheadLimitIssues>true</filterOverheadLimitIssues>
    <heartbeat>
               <notRespondingTimeout>60</notRespondingTimeout>
    </heartbeat>
  </vpxd>
</config>