Server details :
Number of hosts monitored 51
Number of items monitored 1559
Required server performance, new values per second 59.1175

In the Dashboard, the Zabbix server status is oscillating from running "Yes" to "No" everytime I refresh the page ('No' is appearing more often than 'Yes') .
In Administration - Queue I have over 1400 items to be updated for more than 10 minutes (using Zabbix Agent active).

The Zabbix server is running (I see the processes, and the PID from /tmp/zabbix_server.pid matches one of the processes PID) .

The zabbix_server.conf is configured with StartPollers=30 . It is using Mysql backend, with InnoDB as storage engine.
The machine where is running is a VPS with 1 GB RAM, one core.
After I restart the Zabbix server, the queue disappears, but it's growing slowly in the next 24 hours.
Let me know what details should I provide for this issue.
Thanks.

Same problem has been reported on the forums by another user also ( http://www.zabbix.com/forum/showthread.php?t=15936 )