My internet connection via an Airport Extreme and Dratek Vigor 120 Moden has been rock solid for months. About six weeks ago the internet connection dropped with the yellow light flashing on the Airport. It attempts to reconnect, sometimes this is successful, but the drop out will re-occur in a few seconds/minutes.
 
I did all the standard trouble shooting things: checked/swapped cables, microfilter, reset the modem, restarted the Airport, reconfigured the Airport, got the ISP (Talk Talk) the check the line - all showed no fault and the issue persisted. I dug out and re-installed an old Linksys ADSL Gateway and that connects and works fine. Others with a similar fault have confirmed that the connection is solid with the Vigor connected directly to the Mac, but not via the Extreme. The Airport is fine and regressing a couple of firmware versions doesn't fix it.
 
Does anyone have a solution, suggestions or similar issues recently?

I have had the exact same problem at 2 different sites. Both DUAL WAN 2930s with V120s.
They were fine for nearly a year then all of a sudden the internet kept randomly dropping and re-connecting.
I tried every ADSL code available for the 120s but in the end had to swap them for some OLD Netgear DG835 (in bridge mode) the internets been solid since.
It would seem V120s dont like low quality, none ADSL2 lines and low SNR values.