This is very strange.
On my Mac (2.4C2D MBP 15in) running 10.6.4 I have zero contacts showing in my address book. The Mac seems to have no trouble syncing across mobile me and the same contacts show up fine on the me.com website, on my Server and my iphone.
If I do a spotlight search, contacts DO show up in the results list but clicking on them pulls up a blank card.
I've tried reinstalling the app and trashing all the prefs and pulling the data back in from mobile me, but every time the whole address book appears blank.
I've dragged ALL the pref files etc to the trash and stopped mm syncing. When I set up a new address book it lists zero cards. If I add a card it still lists zero cards.
Any ideas?