GETNEXT and genError in AgentX subagent

Net-SNMP version: 5.6
OS: Microsoft Windows XP [Version 5.1.2600] SP3
Command:
snmpgetnext

The problem description. I have created a mib-file with several tables: some_oid.3.1, some_oid.3.2, some_oid.3.3 and some_oid.3.4. In each table on three fields of type Unsigned32. All tables are realised in AgentX the subagent. In tables some_oid.3.2 and some_oid.3.3 there are negative values. At performance of GetNext command the subagent returns genError. Thus the master the agent does not finish processing of query and continues to request the subagent (see RFC-2741 7.2.5.3).

Examples:

1) snmpgetnext -c public -v 2c localhost some_oid.3.1
some_oid.3.1.1.1.1.72 = Gauge32: 78

2) snmpgetnext -c public -v 2c localhost some_oid.3.2
Error in packet.
Reason: (genError) A general failure occured
Failed object: some_oid.3.4.1.1.100

3) snmpgetnext -c public -v 2c localhost some_oid.3.3
Error in packet.
Reason: (genError) A general failure occured
Failed object: some_oid.3.4.1.1.100

4) snmpgetnext -c public -v 2c localhost some_oid.3.4
some_oid.3.4.1.1.100 = Gauge32: 100