Address book and mail problem

So I just noticed something really annoying... 😕😡

I wanted to send a mail to someone this afternoon and when I starten typing his email address in the "to" field... his email address did't auto-complete like it always does. You just type the first letter of the name and a blue popup comes up with his name. But this time it didn't.

So I tried looking him up in address book and notices my address book was complete empty... just like that! more than 200 contacts... GONE 😕 I really don't understand. That was some really vital information in there 🙁

Anyone else had this problem? Or know how I can magically get that info back? I've had my address book and mail both lock up on me yesterday... "application not responding". Don't know why cause I wasn't even using them at the time.

This really sucks 🙁

Thanks for the hint. I checked the cache folder and it's all gone... Only remaining items (also the ones that are in address book) are the standard "apple computers" contact and myself...