I have a Netgear WNDR3700 with both the 2.4GHz (B/G/N) and 5GHz (A/N) broadcasting. I'd assumed that devices connecting on either channel would work together without issues, but there are some devices (such as my iPhone 4 or HP wireless printer) that will only connect at 2.4GHz, and some that connect at 5GHz. However, it seems that they're segregated on the network, so a computer at 5GHz can't print to the printer, but the iPhone can.
This is causing issues not just with printing, but with AppleTV and so on. Is there a way to have the router let these devices all talk to each other?