Have you noticed that pictures from people in your company are not displaying on your Lync even though they show up on others?
To get the pictures back exit Lync and navigate to C:\Users\username\AppData\Local\Microsoft\Communicator\
*Note that AppData is hidden so you can either manually type it in or click to show hidden folders in explorere
In the Communicator folder you will see firstname.lastname@example.org. I would suggest renaming the folder to a .old. Once you rename it open Lync back up and it should now repopulate all the pictures from AD.
Once you verify that this works you can then delete the old sip folder.