I think you are running into what I did with my issue. My DGL would auto-select the best channel also, but I would get very slow speeds, and disconnects. There were a LOT of errors like yourself. 2.4GHz was too congested in my area.

Both of my laptops are fortunate to use 5GHz band, so I have switched to 5GHz 802.11N only. My DirecTV, 360, and Vizio TV is hooked up via powerline adapter.
No more slow browsing/downloading/streaming. I am the only one in my area that is using 5GHz. My laptops connect at 270Mbps rate. Using 2.4GHz, I would only get maybe 54Mbps..

The 2.5GHz channels that has the least overlapping is 1, 6, and 11. When using N, you actually use 2 channels to combine them to achieve faster speeds. You need to check
both channels, not just the main channel. You can find the second channel under:
Status -> Device Info. It's under Wireless LAN.
You will see channel, and second channel. The main channel might have no AP's using it, but how about the second channel?

Hope this helps..