I'm using a AG310 and a TP-Link wireless N router running DD-WRT and have recently had issues where internet just plainly times out.
The Ag310 doesn't appear to switch off or power cycle, but I simply lose an internet connection. Initially what happened was as soon as I tried to use VFX (both outgoing and incoming), after about talking for a minute the entire internet connection would fail.
In terms of trouble shooting, I decided that the 15m telephone cable extension might be a problem and so I temporarily moved the modem right next to the phone jack while I ordered a custom made BT to RJ11 cable.
During this time I experienced no problems at all.
After I got my 7m custom cable and moved the modem and router back to their original position, everything worked fine until a couple days ago. While initially(back when I had the extension cable) everytime I used VFX the same problem would present, now it is intermittent and sometimes the internet connection even disconnects without any VFX activity(it also sometimes works for long periods without any problems).
Xnet did a 24 hour line analysis and noted around 9 disconnections in that period. Many were in the wee hours where there was no internet/VFX activity.
Hope you guys have some ideas.
EDIT: Just observed the AG310 when this happened, first the Internet light goes off, and then the LED for DSL goes off. All other activity lights stay on - few minutes after I hang up phone DSL and internet lights come back on.