I recently had to replace my dir-655 (it got fried by a cable modem). I now have hardware version A4. (Previously I think I had A1).
I used to have 802.11n connections with Mac wireless clients (one an iMac and another a MacBook). However, I have never been able to get that with the new router. I tried both with the firmware that it shipped with (1.21) and 1.32NA, and the same result.
When in g/n mode, everything connects fine (but at g speed). When in n only mode, nothing can connect. I've tried with and without encryption, as well as different channels, but nothing so far seems to get me n speed.
Given the clients haven't changed, it really seems like there's something on the router side, but I'm not sure what to try next.
Any suggestions?