'no active checks on server [] host [] not found' when use proxy

[Onlinehead]

Hi.
I have a small Zabbix server for tests with setup Actions for add hosts when zabbix agent connected to server. And now I setup Zabbix proxy.
So, before, when agent connected to server everything was fine, but after i change 'Server' and 'Active Server' to Proxy address, zabbix agent start to write messages to log like that:

23403:20140530:140038.376 no active checks on server [proxy_address:10051]: host [_hostname_] not found
 23403:20140530:140238.390 no active checks on server [proxy_address:10051]: host [_hostname_] not found
 23403:20140530:140438.404 no active checks on server [proxy_address:10051]: host [_hostname_] not found
 23403:20140530:140638.419 no active checks on server [proxy_address:10051]: host [_hostname_] not found

Zabbix server log:

  5127:20140530:131428.651 sending configuration data to proxy "proxy_address", datalen 59672

Zabbix proxy agent:

 22807:20140530:121428.212 proxy #5 started [poller #2]
 22815:20140530:121428.217 proxy #13 started [poller #10]
 22816:20140530:121428.220 proxy #14 started [unreachable poller #1]
 22813:20140530:121428.226 proxy #11 started [poller #8]
 22832:20140530:121428.233 proxy #27 started [discoverer #1

If i will restart Zabbix Proxy, that problem will fix. I tested it on other host. But it's not very usefull
Maybe somebody known how to fix it without restart and what's heppening with it?
Thanks for help!

[aib]

1) When you change the the options "Monitored by proxy" in the Host description, Zabbix Proxy will know about that after "ConfigFrequency=60" seconds and Zabbix Server will get the data back from proxy after "ConfigFrequency + DataSenderFrequency + Update Interval + small random amount of seconds"

2) The changes of options in frontend and in zabbix_agent.conf file has to be done simultaneously. It's not enough to change it only in one place.

3) You can use the simple form of keyword ServerActive - just IP address of proxy

ServerActive=1.2.3.4

because

If port is not specified, default port is used.