ntl:200 and linksys WRT54GL DHCP problem

[masterdriverz]

I have an ntl:200 modem (and an account with NTL), and until recently used a KCorp Gold series router. Recently I replaced this with a linksys WRT54GL, but ran into the problem that it is not assigned an IP address by the ntl modem. I initially thought this was a hardware fault in the router, but after I sent it back to the retailer and was sent another (which experiences exactly the same problem). I thought it might be the firmware, but flashing it with DD-WRTv24 has exactly the same problem. Manually running udhcpc reveals no error messages, and I have no clue as to what the problem might be. Googling gives nothing useful, and both the old KCorp router and all computers to hand (linux and windows xp, different network cards and cables) work fine. Does anyone have any clues or pointers as to what might be going wrong?

[Aragorn]

to CF
The most obvious gotcha would be 'have you power cycled to modem?'.
If you have, try plugging the Linksys WAN/Internet port into one of the ports on the old router and see if it gets an address from that.

[masterdriverz]

Originally Posted by Aragorn

to CF

Originally Posted by Aragorn

The most obvious gotcha would be 'have you power cycled to modem?'.

Power cycled the modem? Yeah, several times. This is a problem over months, not hours or even days.

Originally Posted by Aragorn

If you have, try plugging the Linksys WAN/Internet port into one of the ports on the old router and see if it gets an address from that.

Yeah, this works, but I really would like to not have to hook up two routers in series, just because of the deficiencies (for no good reason) of one (well, both - the KCorp wireless is broken, hence why I bought the linksys). As I said, the problem is solely between the linksys WAN port and the modem LAN port, everything else works fine.

[Aragorn]

Have you tried cloning the MAC from the old router to the Linksys?
Clutching at straws, but I'm struggling to think of a reason for it not working.