Telephone numbers missing in Lync Client 2010

Hello,

I'm encountering the problem, that most telephone numbers (work numbers as well as mobile numbers) are not shown in the Lync Client 2010. The telephone numbers are entered in E.164 format into the Active Directory, therefore the "Invalid_AD_Phone_Numbers.txt" file is empty. It is a Lync Server 2010 environment. 

Surprisingly the problems do not seem to exist with the Lync Client 2013. So the same user could log in with the Lync Client 2010 and encounters the described problems, but if he logs in with Lync Client 2013 the problems are gone. 

Does anyone have the same problem and/or an idea how I can solve this issue?

Thanks.