After upgrading to ucd-snmp-4.0.1-4 information of network interfaces is no longer shown. From "snmpnetstat -i localhost public" I get the response: "No response when requesting number of interfaces.". I have been using this with ucd-snmp-3.6.1-4 and it worked fine.
This sounds like a configuration issue - the output of 'snmpwalk localhost public' doesn't show any networking info either. Perhaps you need to add more MIBs, or configure some other piece of the SNMP server...? If this sounds like pure guessing that's because it is. It isn't clear that this is a bug offhand. If you visit http://ucd-snmp.ucdavis.edu/#Mailing you can get information on the mailing lists available for this package. The people on those lists almost certainly can provide support and answers.