Does not work on 6.2

I am using this plugin with success on many Nagios instances. However now I tried it against RS818+ with 6.2-23824, and getting error same as man_al describes:
CRITICAL – Problem with SNMP request, check user/password/host
Analyzing this problem, SNMPWALK runs up to.1.3.6.1.4.1.6574.5.1.1.8.9 = 2, then times out.
Timeout: No Response from which following test evaluates as error and exits with exit code 2.