Address Lists, how do they work?

Hi

I have 7000 users on 100 locations. One of the locations complains about when opening the Outlook Addressbook (set to start on a specific addresslist) Outlook freezes and tells that there are no connection to the Exchange server.

How does an addresslist work?

1. Even though you have an OAB, when using a Address List its an online lookup - right?
2. How does it makes the query? AD lookup everytime? Eg. the list is based on a custom attribut.

What can make Outlook react as described? Bad connection from the office to the datacenter?

BR
Steen