DG834G

Can anyone help me ?? I have just upgraded my PIPEX line to a 1MB speed, and
to celebrate I bought a netgear DG834G router modem. However since the line
was upgraded to 1Mb I fail to obtain a sync with the ISP and the modem. I've
changed the modem three times from different sources and still the same.
I've even tested the modem on other lines at friends houses and it works.
Netgear are useless and I must say Pipex not much better. I suspect I have a
problem with phone wiring( done all the usual unplugged everything, changed
filters etc, still the same.) Can anyone shed some light on this problem or
failing that, anyone want to buy a router.
Incidentally my old Speedtouch 510 works on 1Mb fine.

I await some pearls of wisdom from out there.