I have a cable modem from TWC/Road Runner. I believe it's Motorola, but could be wrong (it's at home and I'm at work).
Every fifteen minutes or so it resets itself. It's been doing this for about a year, but never been a huge issue, just an annoyance. If I'm surfing, I might have to wait an extra 30 seconds. If I'm DL'ing, it's not long enough to drop the connection. But now I'm playing World of Warcraft and it's become a maddening experience. WoW apparently doesn't retry a ping. If the connection is lost for a few seconds, I get dumped out of the game.
I will be replacing the cable modem, but I'm wondering if anyone else had had the problem, if you know what causes it, and how to prevent it in the future. I don't think it's a heat related issue. There's plenty of air circulation where the modem is located.