I am having this issue too, but I don't know who to blame: me, Apple, or Microsoft.
Can anyone help me out please?
My home sharing was working perfectly fine until about three days ago. Nothing changed that I know (I know this just doesn't sound right but it's the case!) has changed in my setup.
Itunes is running on a Windows XP PC. I have an iphone 5 and an apple TV (about 1 month old) that have been working with home sharing flawlessly. Iphone 5 has been working flawlessly with home sharing since October 2012.
I updated iTunes to 126.96.36.199 on Jan 7. Everything was still working fine until about Jan 17th.
Now Apple TV doesn't even see the pc is available. My iPhone does not offer up the "shared" library name any longer as it used to when in my wifi zone (I know where to look: under the three dots in "Music" it always became available when I was home and I selected it and all was fine- all automatic and all seemless.
What has happened? I have read posts for days and restarted everything, toglles all home sharing settings, toggled the router in all sorts of combinations. What has changed? Any help at all from anyone would be gretly appreciated!
I have been wokring on this for days and about 20 seconds after posting my previous post, I found the problem. Thanks to everyone on here who contributed to the solution - which looks to have been around for quite a while. It wasn't me, Apple, or Microsoft - it was VERIZON's ACTIONTEC router setting.
I *disabled* the setting (advanced->igmp->enalbed/disabled) and instantly everything worked. There are lots of posts and happy responses to this fix in these forums.
My only questions are 1.) HOW did this value change on it's own or 2.) if it didn't change, why did its "enabled" setting start misbehaving and prevent the Bonjour services from working properly? I am absolutely confident that I did not change this setting manually - I never touch the "advanced" stuff in the Verizon gear.
Anyway, in case you have the same problem, to summarize:
I have a windows xp machine (hanging on to XP for dear life :-) hosting my iTunes 188.8.131.52 library.
iPhone 5, Apple TV 3, and an iPad mini.
I upgraded to iTunes 11 long before the problem started, and the home sharing was working fine for months, even well after the iTunes upgrade to version 184.108.40.206.
Home sharing was working and then unexplainably stopped - copletely stopped. Apple TV acted as if no PC was available at all. I stopped getting the "shared" option on my iPhone and iPad under the "three dots selection" in the "music" task. I had toggled everything multiple times...
CHECK YOUR IGMP SETTING IN YOUR VERIZON M1424 ROUTER! :-)