the router is having a problem establishing a stable connection with your ISP.
Have you tried switching the router off, disconnecting it from the ADSL microfilter,waiting for a couple of minutes and then turning everything back on again?
This will force the router to establish a new ADSL connection and acquire a new IP address from your ISP. It may fix the problem. If it doesn't we'll have to delve a little deeper, but try that first.