Q: Cant get homesharing to setup

What version of iTunes are you running?

What is the other computer?

Possible IPv6 clue...

https://discussions.apple.com/thread/3507281?tstart=0

Verify system requirements

Home Sharing requires a computer using the latest version of iTunes,* and one or more of the following devices on the same home network:

• Another computer using the latest version of iTunes.* You can use Home Sharing with up to five computers.
• An iOS device with iOS 4.3 or later
• Apple TV (2nd generation) with Apple TV software version 4.2.1 or later
• Apple TV (3rd generation)

• *Additionally, you should install any available updates for your version of Windows or Mac OS X.

http://support.apple.com/kb/TS2972