I have lost the ability to sync via Wi-Fi with my iPhone 4. Tried everything but a restore which I am doing just now.
I get a grey circles spinning forever next to the device when it is rarely registered by iTunes over Wi-Fi. This hangs until i try to close the window, iTunes then crashes and I have to force quit.
I have a number of problems with my MacBook and iPhone all due to the updates.
Just so you know you're not the only one, I have this problem as well. It is intermittent. Right now I'm having it so I ended up here searching for a hint to a solution. Apple software is at best C+ with a few exceptions. For some point of reference I'd give Microsoft Windows a D-. I would say Apple has gotten worse for me recently. This is all personal opinion on those points.
I have a few devices. Currently my iPhone and iPad are sitting right next to my computer. My wireless network is strong. I have two AirPort Extremes. My computer is a late 2009 MacBook Pro. I'm running OS X 10.8.2. I've applied all the latest updates and the recent iTunes update 11.0.1(12). I have had the same problem prior to the new iTunes version. Experience after starting to write this...
iTunes running - no devices seen.
Plug my iPad to the computer - iTunes immediately sees the device. Then unplug the device. Device then disappears.
Hit the sync now button on the iPad - nothing useful.
Letting my computer go to sleep then waking it up caused it to find both devices on WiFi.
Restarting iTunes now discovered my two devices and also my wife's iPhone.
So, all in all, I'm not even close to optimistic at finding a consistent solution. Further I don't think Apple will fix it soon. It's gone on for too long.
I agree regarding the quality of Apple software. Recently it seems to have dropped through the floor. I've been running OSX since before the first official release and until Lion it had NEVER actually crashed and that's on many different Macs. Now, it's a disaster and I HAVE to restart every few days or it grinds to a virtual halt. Suggests a serious memory leak, but that should simply NOT be happening with such a supposedly mature OS. And that's not all, but...
Anyway, back to the point. My Mac Pro is connected via wired ethernet to my (Gigabit) network, but its WiFi is also on, largely because it is required in order to use AirDrop with other local machines. The question that then surfaces in my mind is how iTunes connects to the iOS devices. The iTunes setting is "Sync with this iPhone/iPod over WiFi". But, turn WiFi OFF and the devices showing in iTunes remain there, obviously still 'connected'. Yet when the iOS devices have mysteriously vanished from iTunes, turning WiFi OFF, then back ON again causes iTunes to suddenly find them again. So there obviously IS some network shananigans going on that involves WiFi even if it is not actually required. Is this problem in fact limited to those users with both wired and wireless ethernet enabled on their iTunes Mac?
I cannot be the only one to notice from this that the wording in iTunes is therefore actually WRONG. Why do they say "Sync ... over WiFi" when they actually mean "Ethernet". This is symptomatic of Apple's current standards - getting worse by the day.
Sorry, keep getting drawn back to my current dissatisfaction with Apple software. But we still don't have a solution to this iTunes sync problem.
Funny, but I usually keep my computer on WiFi as well as Ethernet. This is because it's a laptop that I bring to work and there is only WiFi there. So I just leave my WiFi on at home.
So I got excited about that being somehow at the root of the problem for me. I then checked my computer and found that I hadn't plugged it in to Ethernet this past weekend. So that during the test I did above I did not have it connected by Ethernet.