First, please make sure you do the test on the Windows host on which the (Local-/Remote-) Probe is installed. Also please double check your credentials and settings.
If this does not help I ask you to do a wireshark trace of the working test with the iReasoning MIB Browser and a trace of the non working test with our SNMP Tester.
After that, please open a ticket with Tech Support and attach the trace-file and also the result files and screenshots of both testers.
Please don't post any traces here, as SNMPv1 and SNMPv2c are completely unencrypted.
Matthias Kupfer Team Tech Support