My girlfriend is using a D-Link WBR-2310. It was fine until she recently switched ISPs and got a new modem. Now computers lose connections to the router if they connect to another network. Her PC stays at home and never has any connection problems. She takes her Macbook to work, though, and when she comes home can't connect to her wireless network. Same goes for my iPhone and iPad, which I bring home and connect to my home network. The Macbook works fine if connected via ethernet. And strangely, if she connects it through ethernet and then disables and re-enables the router's wireless security, everything will connect fine. Until they connect to a different network and then come home again. This is a huge pain to have to do every time she comes home, but we can't figure out how to permanently fix it. Any ideas?
You may want to try the Mac thread, since all of the devices you're having issues with are Apple devices, and there are probably a lot of Mac people skipping over this thread; I'm pretty good with networking stuff, but I wouldn't begin to know where to tell you to look for any of the settings I would normally check.
About the only thing I can think of is do a hard reset on the router, and re-do all the settings.