I have a WR44v2 that has repeatedly found it's way back to me unbootable. There is no activity except for a solid power LED and a flashing Link LED.
Every time it has come to me I have restored it with FlashWriter and otherwise found nothing wrong with it. However it appears if the device is powered down for more than about six hours it will once again become unbootable. This leads me to wonder if there is a dead or weak memory battery of capacitor in there that is failing to retain the software load but I don't have a Torx T10 screw-driver to open this thing.
I have restored it both using TFTP and a serial cable.
I also have two old HSPA ConnectPort WANs and they have never exhibited this behavior.