hello,
I'am running on a zabbix server v 2.0.5 and my zabbix proxy v 2.0.0.
my zabbix proxy is behind a firewall on a LAN, i can monitore the machine who host the proxy zabbix with zabbix agent but a another host on the same LAN doesnt work.
I check zabbix agent log , there is no problem and i have a problem with my proxy zabbix (proxy zabbix log):

12702:20130503:081055.933 Executing housekeeper
12702:20130503:081055.943 Deleted 2038 records from history [0.005436 seconds]
12687:20130503:081056.564 Error while receiving answer from server [ZBX_TCP_READ() failed: [104] Connection reset by peer]

In zabbix frontend , the Zabbix agent stay grey.

need more informations ?

Best regards