2016-05-18 ADDED by zabbix team (zalex): this issue description does not reflect the actual problem, see end of discussion in comments to know what is actually wrong.

After upgrading to 2.2.3 I started noticing lots of the following errors in the console log:

SNMP error: (noSuchName) There is no such variable name in this MIB on some devices (SNMPv1)
No Such Instance currently exists at this OID on some other (SNMPv2)

Examples:
31427:20140416:090657.570 item [sg300-1.apra.it:IF-MIB-ifHCInOctets.[3000]] became supported
31427:20140416:090928.297 item [sg300-1.apra.it:IF-MIB-ifHCInOctets.[3000]] became not supported: No Such Instance currently exists at this OID

31420:20140416:091857.217 item [patton2291.apra.it:IF-MIB-ifInOctets.[8]] became supported
31420:20140416:091857.219 item [patton2291.apra.it:IF-MIB-ifOutOctets.[8]] became not supported: SNMP error: (noSuchName) There is no such variable name in this MIB.

The affected devices seem to be only:
Patton Smartnode gateways: http://www.patton.com/smartnode/
Cisco SMB Switches: http://www.cisco.com/c/en/us/products/switches/small-business-300-series-managed-switches/index.html

The items keep going not supported and back. I have a notification for unsupported items and I received more than 2500 mail last night only.
Probably this devices don't cope well with the new SNMP algorithm in 2.2.3