Login service regularly dies

We have a simple Openfire setup, that works fairly well, except that every few days, it simple stops processing logins (new signins from clients) until the machine itself is rebooted.

I am not yet even sure where to start debugging.

Operating System : Windows 2008

Database : MS SQL 2008

Take a look at the Openfire logs and the memory usage. Maybe there is an OutOfMemory error before the problems begin.