We recently purchased a Cisco 877W for our office, this replaced the 2610 we had there for over 2 years.
The 2610 has always worked flawlessly with any ADSL broadband provider. The 877W however has been shutting down and bringing up the ADSL port on an irregular basis with an audible 'click' coming from the router, making it unusable over the last 2 days.
I changed the micro-filter, adjusted settings on the router such as dsl operating mode and a few other things, all of which I can't quite remember now.
What eventually did solve it for me was the upgrade from "c870-advipservicesk9-mz.124-4.T.bin" to the version 12.4(9)T "c870-advipservicesk9-mz.124-9.T.bin".
Before upgrading I also noticed that the original file 12.4(4)T did not have any date & time stamp like all the other files in the directory structure.
This might have been a corrupt upload by the previous owner.
Whatever the cause, the new file displays the way it should in the directory.
Since then I have had 1 DSL activation (router#sh dsl atm 0) over the past 24 hours where previously I had about 10 to 20 per hour.
I understand that this is not going to be the ultimate solution for everybody, but it might be a starting point.