I didn't mean to insinuate that the problem was any fault of yours, only that the probability of 3 defective routers is less then the probability that there is another cause to the problem.
Granted, a power issue or post issue is pretty clear cut, so it's likely the 1st router died or at-least the power supply did. A disconnect error could have to do with the auto duplex feature though, and the Ethernet port on your modem. Not saying that is likely, but it's a possibility. A possibility I suffered first hand. I had a problem with a DIR-628 and my PS3. My PS3 could connect full duplex to my modem, but it could not connect full duplex to my router. My router could connect full duplex to other PC's, when I later replaced it with the DGL-4500, my PS3 could connect full duplex to that. The theory was the PS3 had a bad port that didn't quite work with the auto-neg method of the DIR-628. Not saying you had this experience, but if I have learned one thing, it's that technology can still surprise you once in a blue moon. Sometimes it's helpful to keep a open mind.