Problem connecting iPod to wifi network with Time Capsule

I have a home wifi network set up with a Time Capsule (v. 7.5.2; simultaneous dual-band, 2.4 & 5 GHz, radio mode 802.11a/n - 802.11b/g/n, set up on radio channels 157 for 5 GHz and 1 for 2.4 GHz, security mode WPA2 Personal; MAC address access NOT enabled).

I normally connect to it only with my Mac (MacBook Pro 15" Core2Duo), without any problems. I've also connected to it with another Mac, and two PC notebooks, without any problem. I've also had 2 people connect to it with their iPhone 4's -- also no problem.

Now, however, 2 people came over with 1 iPhone 4 and 2 iPods (one 3rd gen and one 4th gen). The iPhone connected no problem, but neither of the iPods were able to get a valid connection. To be precise, they found the network and were able to connect, but both received a 169.xxx IP (while the Mac and iPhone received proper IPs). Consequently, the iPods were unable to access the internet…

I tried resetting the network settings on the iPods, and also restarting the router -- without connecting the Mac or iPhone to the router (i.e. such that the iPods would be the first devices to connect to it, in case the problem was too many devices connected at once). I also tried changing the radio channels of the Time Capsule (although that shouldn't be the problem, since the iPods DO manage to connect to the wifi network) -- all to no avail…

I'd be very grateful for any suggestions anyone may have! Thank you.