Did you try the steps that I suggested? As a temporary work-around  please set the Internet Explorer’s caching settings for systems behind this circuit to not check “Automatically” for new pages, but to check on every start up of Internet Explorer? NAD error 2902 occurs with dry-line IP DSL which doesn’t require filters.  AT&T is aware of the issue and unfortunately there is no fix at present, but they expect to roll out a firmware update in the very near future to rectify this. I have never tried but I just wonder if it would work miraculously well with the usage of a filter even without any phone service.