I have to stick my two cents in here. I also have the problem between my iPhone 4gs, my iPad 3 and my new Mac Mini Server (Mountain Lion 10.8.4). I can go through all the gyrations listed above and maybe the wifi connection will work, maybe not. Actually, mostly not. Actually, not.
The kicker here is that I'm on a University wide wireless system, maintained by our IT dept. And the wireless signals are strong and reliable all over campus. My phone and iPad and Mac work fine for every/anything else wireless that I want to use them for. But iTunes can't or won't make the wireless connection.
By the way, same phone and iPad connect flawlessly with my home Mac, a Mac Pro running Lion through an IP provider supplied router. I've never had to touch the router.
Any ideas? Sure, I can connect by USB, but it's inconvenient and I SHOULDN'T HAVE TO.
Abbe