Always a network problem

["Brian Ackermann" <brianj@subrad.com>]

Ok guys, lets see if we can pound out a new network issue here...

I've got a linux box (RH5.2) on our network.  Network has two subnets, 14 real
IP addys, and a NAT class C.  My box is on the real subnet.  Last time I touched
it, everything wes working just fine.  It could speak to the world, and any
computer on either of our subnets.  Then, after a few days, the internal
computers can no longer connect to the 5.2 box....

No settings have changed anywhere, so far as I'm aware, but after a few days of
working, it ceases....

What must I do to get these machines on speaking terms again?