OWA Is up *most of the time*

hey guys, here is a weird issue we are having. owa 2003 is a front end server with 2 backends.
i remote desktop to home from work to monitor the status of it via ping.
for the most part pings come by fine, however there are maybe a few times every hour where for 2-3 minutes the mail server becomes unpingable, hence no OWA.
the mail server obviously has 2 nics, 1 directly outside via firewall, and 1 internal.
Through one of these “bumps” i logged into the firewall and was able to ping both interfaces of the mail server and outside to my home pc, but not backwards.
whats happening here?