NT Server 4.0 Shutdown

Over the last 3 – 4 weeks my NT server has restarted itself several times, has anyone got any ideas. I thought it maybe something to do with my Tripplite UPS / PowerAlert software. I have no ideas, I’m not seeing anything in my Event Logs,, and non of my other servers are shuting down, but they all use other UPS’s. On this server I have Proxy, Exchange, Norton AV CE 7.0, and poweralert.