I too am having the issues everyone else is. I have a DLink DIR-655 and a 2nd Gen iPod Touch. I've tried everything anyone suggests in the thread as a possible fix and none work...
Interesting, if I leave my iPod plugged in it will maintain a wifi connection all the time. As soon as I unplug it and lock the Touch, then unlock it it takes several minutes to get it's wifi connection back...
Joining it to my wifi was a complete nightmare. I had to continually click the join button until finally it joined the network...
I've given the Touch a reserved IP, my router is configured to accept all types of connections (N, G, B) and different types of encryption protocols (AES, TKIP) and I too am using WPA/WPA2...
I sent a support request to DLink in hopes that potentially there is something they might be able to do from the firmware side but, I haven't heard a peep... I assume you all have contacted Apple...
This really needs to be addressed...