iTunes Wi-Fi Sync - option greyed out

Since I update iOS software to iOS 6 on my iPhone 4, the 'iTunes Wi-Fi Sync' screen on states 'Sync will resume when "HENDO" is available".

"HENDO" is a previous Windows PC I had, but I have been syncing with my new Macbook Pro, which before the software update, the iPhone 4 recognised my new Mac name, but since the software update it has reverted back to a previous PC.

Option for 'Sync over Wi-Fi' is ticked on iTunes.

Also the 'Sync Now' is always greyed out. iTunes does recognise the iPhone and you can initiate the sync over Wi-Fi from iTunes, but can't from iPhone.

Does anybody have any ideas? Is there another setting I need to have on the iPhone or iTunes?

Any help would be much appreciated