I can across this warning while logging into the Lync 2010 client with a recently created account.
“The address book is preparing to synchronize. Search results might not be current”.
The issue here is that the Lync client does not download address book immediately and checks for GAL changes between 1 and 60 minutes. As this is a new user account, we can force the address book download to speed things up. There are a couple of steps that needs to be completed.
Update Lync Server Address Book
As it is a new Lync user, we need to make sure that the address book on the server is updated. Run Update-CSAddressbook in the Lync Shell.
Registry Edit On End User PC
Second is to make sure that client downloads the address book immediately. We need a registry edit on the client to force it to download the address book immediately. Run the following from an elevated command prompt.
reg add HKLM\Software\Policies\Microsoft\Communicator /v GalDownloadInitialDelay /t REG_DWORD /d 0 /f
You can create the DWORD and set it to zero manually as well. Create the “Communicator” key if it doesn’t exist.
Delete Address Book Files From User Profile
Third is to delete the address book files from the user’s profile so that Lync client must download an address book from the server. Delete Galcontacts.db and Galcontacts.db.idx.
If the end user has Windows XP, the files are located in %userprofile%\Local Settings\Application Data\Microsoft\Communicator\sip_username@domain.
If it is Vista or Windows 7, the files are in %userprofile%\AppData\Local\Microsoft\Communicator\sip_username@domain.
After the three steps above, the user will have an updated address book while logging back into the Lync client.