This thread is over a year old, yet I can confirm the issue.
I am seeing the same error message on VMware ESXi 5.0.0.
When vicfg-snmp is run with the --verbose option I can see the following response from the server:
RESPONSE: $VAR1 = '<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<RetrievePropertiesResponse xmlns="urn:vim25"><returnval><obj type="HostSnmpSystem">ha-snmp-agent</obj><propSet><name>configuration</name><val xsi:type="HostSnmpConfigSpec"><enabled>false</enabled><port>161</port><option><key>EnvEventSource</key><value>indications</value></option></val></propSet><propSet><name>limits</name><val xsi:type="HostSnmpSystemAgentLimits"><maxReadOnlyCommunities>10</maxReadOnlyCommunities><maxTrapDestinations>3</maxTrapDestinations><maxCommunityLength>64</maxCommunityLength><maxBufferSize>1500</maxBufferSize><capability>COMPLETE</capabil';
The message is truncated and therefore is not a valid XML. This is the response to the basic request
ha-property-collector->RetrieveProperties(HostSnmpSystem)
This request is issued before any of the snmp commands can be executed, therefore vicfg-snmp fails on all commands.
I would like to investigate this further.