What version of the agent do you use ?
This is a known issue. You can try a never ESX agent or disable these events in SIM.
The second option you would have to configure in de MIBS. The disadvantage to this is that if you run a MIB update you would have to set this setting again as the mibs will get overwritten. The second solution you should try first as that is the real solution and the second is a fix. For the second option you log into SIM go Options >Events> SNMP Trap Setting.
Select he cpqhost.mib undr Mib name, Select cpqHoMibHealthStatusArrayChangeTrap and set Enable Trap Handling to No.