I have a network setup with an Airport Extreme base station, and a second wired bridge access point with the exact same SSID, key, etc., that's running DD-WRT v24-sp2.
With my iPad 2 with iOS 4.3.3 and 4.3.5, my wifi connection won't work after x minutes of use. It looks like it's connected: icon is good, IP address is good, but no traffic. Turning wifi off and then back on instantly repairs the connection.
However, it always works when I'm close to the Airport Extreme.
I filed this bug with Apple a while ago, and they've asked for more information, but haven't fixed it yet. I wonder if anyone else has this issue...