For some unknown reason my address book (Snow Leopard) lost its synchronisation with my iPhone. Firstly it stopped updating things, and then it got to the point where I lost all the contacts off my iPhone (thankfully I had them backed up) and it would no longer sync between my iPhone and iPod and Mac computer.
I talked with Apple, they couldn’t help. I spend over and hour with the mobileme chat line, and subsequent e-mails and in the end I gave up.
This week I came across this great article which fixed everything! If you’re having issues with Apple address book definitely give this a try.