Router won't connect to ADSL

Hi, Not sure if this is the right area or not... Our ADSL broadband went down a couple of weeks ago. The ADSL light on our Linksys wireless router/modem went out. Anyway, after a fair bit of faffing and fault checking, a BT engineer came to our house last week and fixed a problem with the line. He proved that the ADSL was working by connecting up our ancient Speedtouch modem to it. It works absolutely fine. But our Linksys router was still having the same problem - no light on, no internet connection.

We assumed the router was now faulty (co-incidental with the BT fault!) and reverted to an older Belkin router. But had the same trouble with this. We have checked and rechecked settings, checked details with our ISP, re-input settings, do factory default restrores and even upgraded the firmware on both. But no luck. My ISP suggested that both routers were faulty and that we should get a new one. We thought this was unlikely but couldn't find a reasonable explaination as to why the Speedtouch modem would be working but the routers not even finding the ADSL.

So... (I do eventually get there ;-)) I bought a new router today. And guess what? Same problem. ISP has asked me to take them all to my friends house tomorrow and try them there to confirm they aren't broken. But they're baffled. And they're also not sure what to log the complaint to BT as as we technically have working broadband.

Any thoughts or suggestions? TIA