This document describes the Java recommended settings to avoid problems that may occur with the different java versions.
Open the java settings
The Java settings are accessible from the Control Panel
Security settings
Add the URL of the server in the Exception site list.
Example in the screen shot :
server address : 192.168.1.1
Port : 11155 (default port for Hivision 5.1)
General settings
From the "General " tab, select "Settings"
Delete Files ...
Unselect "Keep temporary files on my computer"