Belkin N1 Router started having high ping/ slow connection

[netlon]

Hi there. Win XP Desktop, VM 20MB BB, Webstar 100 modem. I bought a Belkin N1 Router F5D8231-4 a couple of months ago and have a desktop (wired) plus a laptop (wireless) connected to it. I went to play COD4 a few days ago and all servers had pings starting around 450-500ms. Usually they start around 35-50ms. My first thought was #@?+ing Virgin again.....but first I tried connecting direct to modem and ping had returned to normal so BB connection must be ok. I've updated firmware on router, restored factory settings, reinstalled router from cd set up. I've talked to Belkin twice who just talked me through what I have already done. Ping test to bbc.co.uk give an average of 450ms when using router and 35ms when connected direct to modem. I've tried powering down both router and modem. Anyone got any help or advice please. TIA