I got it to work last night by using the browser control panel to connect via WPS PBC on BOTH units.
Previously, I tried WPS using the browser on the 815 and the physical button on the 1522, and also manually entering the encryption info. Neither worked, even though it said it was connected in both cases.
But, using PBC thru software seems to have done the trick. And, now that I think about it, I had a hard time getting it to work with the 2Wire Gateway, as well, until I used software PBC in both units at that time too.
I think the issue may have more to do with the 1522 than the 815.
FYI, I am going to try the Media Bridge from TrendNet, and the 2AN34D from Encore, which can work as a router, ap/bridge, or repeater, and compare them to the 1522 and 815. They are only 2.4GHz. But, I've never had an issue with multiple streaming and data over that band with my 2 Rokus, GoogleTV, 2 networked BD players, 2 networked Dish receivers, networked TV, and 6 PC's which also stream Slingbox.
A good 2.4GHz N300 signal is all I need. Living in a single-family house, I'm not bombarded with 2.4GHz interference. So, I got that goin' for me...which is nice.