With firmware 6.00 in a Netscreen SSG5, I encountered an odd bug where available sockets for the management web interface run out, because they're not being freed properly.
Rather than rebooting the thing every once in a while, there's a way to free used sockets through the console.

Your best bet is to attach a serial cable to a server or something and use HyperTerminal (or another terminal application) to access the console of the Netscreen.

Once logged in, use the following to get a list of sockets in use:

get socket

This shows a list of in-use sockets, along with their ID. Sockets with   ...