I also had an RT31P2 which, at best, was flaky. I also had one while I was with Vonage. It worked great for about 6 months, then died a slow death.

Support confirmed that the RT31P2 provided was abnormal (they couldn't connect to it even when it wasn't behind another router). I was sent a PAP2T replacement, which worked fine for about a week, then it too started losing authentication all the time. Another PAP2T appears to have resolved all my issues (sitting behind a Linksys WRT54GL running DD-WRT).

-Craig