Hi, this may be a bit too late but after months if not years I have managed to get my wifi sync working with my win 7 pc. I have bt home hub 4 (which has dual band 2.4 and 5 MHz wifi signal.
I looked at loads of solutions. None of them worked for me. I had tried amending the firewall settings, amending deleting and reinstalling antivirus settings on the basis that something kept 'blocking' my iphone from syncing with the pc. I had fiddled with ipv6 settings, had previously closed and restarted itunes related services via task manager - all to no avail!
My itunes would (for the first 3 or 4 seconds) connect as the iphone name appeared and the dots swirled to show it was connecting. At this time in iphone general wifi sync settings the text would go blue as if ready to sync. But then would grey out - not connected after all. My only option was to sync via the usb cable.
Here are the changes I made and eventually (months of fiddling) I'm completely up and running!!
This is in no particular order and apologies this is from memory... Some of these steps will be completely not applicable but wanted to document everything I did.
1) I changed the name of my computer via control panel - I also reset and renamed the workgroup. I also changed the name of my iphone (whilst wired connected to itunes).
2) after amending loads of windows firewall settings I eventually reset to default! This prompted a number of programmes to warn me it was 'blocked' and I had to 'accept' these programmes and automatically amend firewall from blocking.. I'll come to this later.
3) uninstalled and reinstalled my antivirus. All back to default settings.
4) ran a free registry cleaner... It deleted a number of incomplete items such as firewall commands that were not applicable.
5) reinstalled Itunes - manually installed 'bonjour' again. By downloading and unzipping itunes and clicking bonjour only. This guaranteed that it was installed and working.
6) (still didn't work at this point but here's where it all changed! I amended my router set up. Firstly I had two different names for the different wifi bands. 2.4 named different to 5 MHz because I only had my iphone 5 connecting to the 5mzh. This was for better wifi connectivity. I reset and ensured upnp etc was set to on. I then under the 5mhz settings menu I ticked the option for each band to share the same name etc. I still have 2 band wifi with the recommended security settings etc. But the name only appears one in my wifi settings now! (I forget the exact options but something like 'sync the two bands together' or similar.
7) I clicked on itunes settings to share files music etc on my home workgroup (not that I have a workgroup- no other pc's etc) but after clicking this a warning appeared that never popped up before saying "FIREWALL IS BLOCKING SHARING- do you want to amend firewall and allow sharing' or similar words. - that's the first time that ever appeared and due to resetting firewall to default settings.
8) STILL DIDNT WORK- then I rebooted my home hub. Unlike normal it too AGES to reboot. The lights on the wifi went yellow and flashed, after 2 or 3 attempts it connected to my iphone and I put the password etc in again to connect.
9) shut down pc rebooted and oh my god... Ever since wifi sync has worked. I booted up itunes... Normal swirling dots but this time my iphone name STAYED. I pressed sync and it worked! I have done this each day for the last few weeks and it works perfectly. Not sure which of the above fixed my issue but I'd guess it was wifi router settings and the resetting of my firewall that prompted the new rules to be applied.
Just hope this helps other people!