ZABBIX Agent not sent data

[watto]

Hi!
I 'm monitoring about 20 windows servers, but some days ago i find, that 3 servers are stoppend send any data to zabbix server. I didn't any change in configuration of agent and server. No error in zabbix_server.log, but in the zabbix_agentd.log:

4640:20081210:095245 Getting list of active checks failed. Will retry after 60 seconds
4640:20081210:095345 get_active_checks('192.168.28.250',10051)
4640:20081210:095406 Get active checks error: *** Cannot connect to [192.168.28.250]:10051 [A connection attempt failed
because the connected party did not properly respond after a period of time, or established connection failed because c
onnected host has failed to respond.♪
]

What can i do?

Thanks.

[watto]

ZABBIX Server 1.6 (Freebsd 7.0)
ZABBIX Agent 1.4 (Windows Server 2003)

[watto]

If I create in ZABBIX new host with same IP address and items - all work fine. What's the problem?

[watto]

One more stuff:
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
2352 zabbix 1 123 5 8432K 4228K CPU1 0 118:36 98.97% zabbix_server

Any ideas?

[watto]

I change the port in zabbix server config - all work fine. So:
- If you create another host with same parameters - all work fine,
- If you change the zabbix server port - all work fine.

Why??? Its a bug?