I just upgraded from 2.0.8 to 2.0.10 and got a lot of "Cannot get socket IP address:  No error: 0" messages in zabbix_server.log. Seems like it's related to active checks.
Zabbix server is compiled with IPv6.
But I tried to recompile zabbix-server without IPv6 and message storm has gone.
Probably the problem is in src/libs/zbxcomms/comms.c (maybe in lines 1095-1104). Sorry, I have poor C skills.