[GreenMachine]

I too am an owner of an Ntl home 100. I bought a belkin wireless G router to connect my PS3 to the internet. I did suffer the exact same problem as yourself and am currently suffering a very slow connection.
I was connected to my modem by USB which didn't help a great deal when trying to install the thing as this belkin router only operates by ethernet. After a couple of frustrating days and some swatting up on the troubleshooting page and this fourm (as I am no tech expert) I took some advice as Rob has put it;

Power off everything, PC, router, modem.

unplug USB and ethernet cables from modem

connect only ethernet between router WAN and modem

connect PC(s) only to router LAN (ethernet or wireless)

Power on modem (let settle)

Power on router (let settle)

Power on PC(s)

It required a lot of faffing around but eventually worked and worked extremely fast... for about 5 days. Now I have been experiencing extremely slow internet connectivity over the weekend to the point the PS3 is unplayable and my Pc's browser is running like a 56k modem. So i'm back using USB with no router.

I repeated the powering off procedure and its still slow. I then connected the ethernet cable from the modem to the computer directly and its still slow. So I am guessing this is either a problem with the ethernet cable which is not an Ntl one (Aquired off an engineer in work last week, quite old last tested 2000 lol) or it is a problem with the modem.

I'm ordering a new ethernet cable tonight and if this doesn't improve things i'm going to ring virign and blag a free modem upgrade... cause its pretty old.

Hope this was some help, I know it probably wasn't, but at least you know there's at least one person out there in the exact same boat. Goodluck. Keep me updated