ok, back again - to reiterate, i have a 655 A2
I've pretty much narrowed down the issue to my NIC. it's a realtek gigabit RTL8169/8110 chipset.
i believe there is an issue with their driver newer drivers, versions 5709+. i'm not sure what the driver version was before that. there is a new driver realtek just put out in the last week, 5712, which i was hoping would fix the issue, but it does not.
on the 655, i've tried several settings. wireless on/off, etc etc etc. it will still disconnects on the lan side randomly.
i plugged into the embedded 10/100/1000 Intel NIC i have on my motherboard (for w/e reason, the 655 will never recognize it as a gigabit nic and always connects as 100mbs), and i have left it like that for over a week now and not one disconnect. if i go back to the realtek card, it connects at gigabit, but the random disconnects return.
i know the nic isn't bad because i tried using an old dlink di-604 i had sitting in the closet and it connects @ 100mbs and was solid for over 2 days straight on the realeak card.
i have not tried the realtek nic in 100mbs mode on the 655, but all my other equipment is gigabit, so no point to try that for me since i know it works in 100mbs on a different router just fine. hopefully dlink will find what the issue is with these newer realtek drivers and fix it.
in the mean time, i'm ordering a zyxel x550N router with gigabit switch to see if it's simply just the realtek drivers or if it's the actual router. i'll report back after testing. should be sometime later next week.