SBS 2003 Server down - no clients can attach to it and retrieve DHCP or use resources from server

sbs2003 server - clients cannot attach to the server - the domain is not available - they can't ping the server network card - we have changed out network cards, used a cross-over cable, etc... the connection issue appears to be related to dns and dhcp - there is an error event id#20169 in the event viewer - unable to contact DHCP server.  The Automatic Private IP address 169.254.239.205 will be assigned to dial-in clients.  Clients may be unable to access resources on the network.  DHCP client and server are enabled.  I went to the add/remove components, removed them and then re-added them.  I reconfigured the dhcp scope, etc...   The server can surf the internet, we just can't attach to it from the cals - I have tried giving the clients a manual ip address and that still does not allow us to ping the server.  The server was running fine last week, but they could not send out of dispatch to their phones on the server. They recently had the cable modem changed out so I had to call and have NAT & DHCP removed from the unit.  So, afterwards we had the client reboot the cable modem, firewall box and the server.  The server came back up but they have not been able to attach since then (last Friday afternoon).  We came back onsite this morning and found that the server disk space on c: was 294mb.  We cleaned up temp files, etc.... now we have 3gb free on drive c:   So, we are not sure if the reboot caused a problem with low disk space??  Anyways, DHCP and DNS seem to be corrupted.