Home sharing does not work in iTunes 9??

Question

I have spent hours going through this and conclude there must be something up with home sharing in the latest iTunes - I had no problem with it previously.
I have everything checked that should be checked, my iMac and MacBook are on the same local wireless connection and it's fully functional. I can manually transfer files if I want.
File sharing is on, home sharing is on in iTunes and "share entire library". "Look for shared libraries" and "share libraries on local network" is checked in both computers. I am logged into the iTunes store on both computers.
But there is no shared list in either machine, and in iTunes > Preferences it says "No users connected" - even though both computers are connected to the network. And it makes no difference if I log in to one or both computers and mount the volumes or not. Nothing will make it work. Rebooting, quitting iTunes, switching home sharing off and then on again, clearing out all my old passwords in Keychain... nothing. Any suggestions welcome.

Answer 1

HALLELULAH!
Well thanks to everyone that tried to help with this. I can't believe it has taken me two whole weekends to sort this out. And yes I did go to my local Apple store but they said that everything I had already done was what they would have suggested - they were interested to know as well.
Pretty sure this is not any fault with iTunes. What I had to do, finally, was completely wipe the HD of my MacBook, clean install the original software, register it, update it, reinstall all the other software I needm register and update it, reset iSynch, Mobile Me etc. etc. Finally, after everything else was done (about 12 hours work), I imported all my music and playlists into iTunes, fired it up - and the Home Sharing worked straight away first time!!!!!
Peculiar thing is that in iTunes > Preferences > Sharing at the bottom of the window, it still says "Status: no users connected" on both computers". Even though the Home Sharing is on and running and the shared libraries are all visible and working. Unless that's something to do with password settings, I don't know (I don't use any password setting on iTunes sharing as it just "I, me and myself"). But I don't care, IT WORKS!!!
Along the way I also reset my router a couple of times, but I think the route of the problem (no pun intended) was not that. What I would definitely very strongly recommend to anyone is, whatever you do, don't use Migration Manager to copy all of the stuff on your desktop computer onto your laptop (which is what I did a week ago after installing a new drive and more ram so I can run Logic Studion on the MacBook). Doing that caused the most incredible problems, of which Home Sharing turned out to be the least. All kinds of weird stuff was going on and the MacBook became increasingly degraded in performance, the network was going nuts, until I was forced to take the drastic steps above. The solution was to start again (NOT with Migration Manager) installing everything from DVD or manually dragging it across item by item, registering and updating... hence the ludicrous amount of tme I have just spent on this.
It's great when it works