Zabbix 2.2 stops gathering information from Devices

[AllertGen]

Hello, everyone.
I'm getting some strange problem with Zabbix 2.2. After some time (it can be 20-40 minutes or after some hours) zabbix is stoping gathering information from devices (but not from all). At this time "busy" status of Zabbix unreacheble poller going to 100% from 0%.



Log data:
31282:20131209:152550.806 SNMP agent item [.1.3.6.1.4.1.318.1.1.1.4.2.3.0] on host [######] failed: first network error, wait for 15 seconds
31398:20131209:153827.042 executing housekeeper
31398:20131209:153827.047 housekeeper [deleted 0 hist/trends, 0 items, 0 events, 0 sessions, 0 alarms, 0 audit items in 0.004324 sec, idle 1 hour(s)]
[END of log file]

It returns to normal only after manual restart of Zabbix-server.

I've tryed to change values "StartPollers", "StartPollersUnreachable" in zabbix_server.conf but there is no effect.

I can't undenstand why it stopping gatering any information.


Some info:
OS - Ubuntu server 12.04.3 LTS.
Zabbix installed by manual here (deb file + dpkg + apt-get).
Information from devices gathering trough SNMP v3 agent.
Right now I have at monitoring 4 devices and this problem appers only with 2 of them.

Thanks for advices in advance.

[AllertGen]

Solved problem by changing OS to CentOS. Don't know why in Ubuntu server poller don't want return to monitoring after loosing connection to device.