as per posts below, my subnet is also 255.255.248, and my router will no longer connect via modem, but pc will connect via modem.
really pleased i have found this thread, as i have only just ventured into the world of networking at home (literally last week), as was convinced either:
a) I was dumber than i thought!
b) my new Netgear router was fooked!
like ubermik, phoning telewaste is a test in patience and unfruitful outcomes...
in case it makes a differnece to those experiencing this problem, I live in Solihull (maybe a geographical issue with telewest?)
i'll continue to watch thread for any updates - the thought of having to continually reset the router settings to keep pace with the IP address leases is a 'bridge' too far (sorry, sorry....)