If DNS fails, it often looks like DSL is down to the user.
I assumed the DSL is dropping. Modem says 'DSL Uptime: 0 days 3 hours 0 minutes 7 seconds' which co-incides with today's drop out.
Line Status here (hopefully it copy/pastes ok!)
TCM(Trellis Coded Modulation)
Can you check again later in the day to see how often it is dropping - is it just once per day, or is it more often, and you just hadn't noticed?
Can you position the router so you can see the DSL / Internet lights go out during the disconnect situation?
I had a similar situation. No problems with internet speed. Connection would disconnect multiple times typically at night / peak times.
The number of disconnections would be just under the amount that ISP would get chorus to investigate.
For me, I replaced the phone cable and seemed to have fixed (fingers crossed). But that could indicate a fault with either my modem jack point or DSL wall jack point.
Also 2degrees support person make a good point about to many devices connected to same power point as router. i.e. Router / modem behind TV with many devices, power demands could cause... maybe.
Also you should get your ISP to do a line trace for 24 hours to gauge the number of dropouts.
Thanks for all the help and suggestions so far. I just checked the DSL Uptime today and no drop out this morning at all. DSL Uptime: 1 days 9 hours 24 minutes 51 seconds.
I will keep monitoring this. The only thing I changed was to turn off the daily screensaver downloading on the Apple TV. I doubt that that makes any difference but noting it anyway.