I confess I am not as well versed in Routers as you seem to be, so I have a question.. I only suggested he flash ddwrt in an effort to fix his issues..
Have you ever seen a Firmware upgrade/update fix an existing issue with a router? or is it a waste of time if you are already having issues?
I had a Dlink or Netgear, don't remember which that would send out a wifi signal but wouldn't push through the internet signal. Same problem the OP seemed to be having. I flashed ddwrt and it started working again. That's just one experience, but it can make a difference.