USB modem will happily connect to internet, 3 routers refuse to.

Title is the TL;DR version, i have three wireless routers, D-link, Netgear and a Safecom, and all three refuse to connect to the internet.

This started tuesday day, where my internet connection dropped, on trying to re-connect, the router said it could not find a DSL line to connect to, so i tried the other two, same problem with them.

So, i tried my USB modem (Speedtouch 330) and it connected without a problem. It still connects happily, but all three routers still are unable to find a DSL line.

Ive been in touch with my ISP (Demon), they tested the line and foind no problems, watched as my modem sync'd with the remote server, then accepted the internet connection...But all three routers were not initiating a sync.

Ive tried resetting all three routers, updating the information my ISP provided me with, tested all three routers on a friends internet connection, All three worked without any problem, Replaced all wires, replaced the ADSL splitter...Everything, even removed the front panel of the phoneline socet to use the hidden one with in...Nothing what so ever will help my routers to find my DSL connection.

also tried isolating the line, only using the ADSL splitter and the DSL line, also disconnecting EVERYTHING to do with the internet connection, even the phone and damn computers.

thing is, when my connection dropped on tuesday, i was the only one in the house, on the remote computer (using the wireless network, obviously), playing World of Warcraft...nothing else.

What i dont understand is that my ISP has changed no settings, no settings have been altered on my routers or network configurations...Everything has just randomly stopped.

Has anyone seen this problem before? all the avice ive seen so far is to reset configurations, and start again. Ive done everything put towards me, and nothing works.

If there a difference in information sent between a router and modem? is there any whole harted reason for this to actualy happen? Besides my ISP, Router Menufaturers, and BT...Is there anyone i can talk to about this?

Any help you people could give me would be greatly appreciated, as this problem just seems completly improbable.