Does the iPhone connect to the internet? I had a similar issue and found a great article called "Take control of your 802.11n Network". I found it when i was having endless and bizarre problems with my wireless network. I read an article where a university IT department was starting to have all sorts of weird issues with their wireless network system in the dormitories. Turns out, the iPhone's (which were becoming more and more popular with the kids) were screwing with the network, stealing odd amounts of bandwidth. Both my girlfriend and I have iPhones and each have a laptop. Her laptop is a G wireless card, mine is an N. Also have a PS3 and an Apple TV connected.
With the newer N routers, they can come configured incorrectly from the factory. There is an N + G mode, where it essentially dumbs down the N broadcast to the 2.4GHz spec. This apparently can cause weird problems. The internet worked on our iPhones, the G wireless laptop and the PS3. No go on my Apple TV and my N laptop. Only way I could get it to work 100% flawlessly was to have two separate routers (this was before they came out with dual mode, dual broadcast routers). So now I have one router that is set up to broadcast N only, and the second is connected via ethernet and is broadcasting G only. Everything works perfectly.
I also found it interesting, if you are running a Mac, to check out istumbler. Its a great program to show you the signal strength you are getting for each network you see, as well as show you the channel numbers the neighbors wireless set up is broadcasting over.