I was convinced my issue was with DNS and DHCP, but it turns out that it was something I found by pure luck. I have Crashplan running on my HDA and this was consuming all of my bandwidth so the pings I was using to troubleshoot essentially never made it out because there wasn't much bandwidth left. ...

Yes, so what I did is turn off DHCP in my router, set my DNS server to the IP address of my HDA and turn on both the DNS and DHCP server in HDA. Is this the correct way of setting it up?

Are you using the HDA as the single DHCP and DNS server? Check the client to see if it's using the HDA for both.

Sorry, I'm not sure what client you mean.

I know this is a really old post, but I am having the exact same problem. I've tried different modems, different routers and it all points back to something with DNS on Amahi. Anyone else ever see this or have a solution to it?