Hi Giovanni,
Could you please verify the data which is returned by the router by either using the following command on a box which has an snmp client like net-snmp installed:
snmpwalk -v 2c -Ox 1.3.6.1.4.1.9.9.42.1.2.2.1.2
If you cannot use such a client, maybe you could take a capture of the snmp traffic?
The whole point here would be to see if the data send by the router is wrong or if the interpretation of the HP software of the data is.
If you still see this 2.0.0.0 value with those two means, this looks like a software bug on the router and I would advise you to open a TAC case for having it investigated.
Regards,
Nicolas