Problem with Windows agents

[happyjoe]

Hello!
I have problem with Windows workstations (Zabbix agents installed).
After some time Windows workstations stops sending monitoring data one after one (status of hosts are 'Monitored' and 'Available', items are 'Active').
Zabbix agent service OK. After Zabbix service restart no changes.
I have 1 Linux server - no problem. Some Windows servers stopped show data already 3 times in 30 day period, some - 2 times and 1 server - 1 time.

Solution was Zabbix server restart, mysql restart and increased connections limit (if I remember right?).
But problem repeat

Standard zabbix_agentd.conf:
Server=192.168.0.0
ListenPort=10050
DebugLevel=1

Any ideas, please? I cannot process Zabbix implementation, if this this problem exists.

Zabbix agent log (last):
]
1080:20080611:070414 Before read
1080:20080611:070414 In parse_list_of_checks() [ZBX_EOF
]
1080:20080611:070414 In disable_all_metrics()
1080:20080611:070414 Parsed [ZBX_EOF]
1080:20080611:070414 In process_active_checks('192.168.0.0',10051)
1080:20080611:070414 In get_min_nextcheck()
1080:20080611:070414 Sleeping for 60 seconds
1080:20080611:070514 In process_active_checks('192.168.0.0',10051)
1080:20080611:070514 In get_min_nextcheck()
1080:20080611:070514 Sleeping for 60 seconds
1080:20080611:070614 In refresh_metrics('192.168.0.0',10051)