I realize this is an ancient thread, but I was looking for info on the Central serving Receivers, and couldn't find what I was looking for. Maybe some more advanced future civilization will find this and wink knowingly about it...
Although it appears the Central might be capable of serving DHCP if hacked properly, apparently it does not do this--my sole Rio Receiver always gets an IP address from my server box (presently a Magnia SG10) in the range of 192.168.1.120-125 (along w/a few other gizmos I have that need DHCP).
Since Rio had to assume it would have some customers whose only network would be a Central and one or more Receivers, they must have planted some way to deal with this, i.e. maybe if the Receiver can't find a DHCP server on the network, it takes on a 169.x.x.x number and by some other magic (hey, I'm no TCP/IP expert!) establishes communication with the Central.
Dunno what the original poster's problem turned-out to be, but I'd guess his DHCP server was down at some inopportune moment, or a hub/switch failure occurred somewhere, and the Receivers got confused about it.
I wish the Central served-up DHCP since it is on 24/7--maybe some day when I've become a self-taught expert on Linux I will hack-in to it and make that work...