I returned the first router this happened on. After getting the replacement, I restored the settings I'd backed up from the first one, and it happened on the replacement shortly after putting it to use.
I got ahold of tech support, and they suggested resetting it, and if it worked, not restoring settings, but putting them in manually again. The reset got the wired connections working again, and I put the settings in manually. The settings are VERY basic...probably 5 statically assigned IP addresses, 4 or 5 port forwards, a cloned MAC address, and that's it.
That lasted a few weeks or so, but then a couple of days ago, it happened again. I backed the settings up, reset it, and restored the settings. It lasted about a day and the wired connections stopped working again.
This is obviously a software problem, but I'm admittedly confused as to why others aren't experiencing it. Maybe they are and aren't posting it here for whatever reason. I'll go through the reset and MANUAL application of the settings again, but does anyone have any suggestions on this? Is there detailed logging that might catch something to pay attention to?