You have Lync running and open a SharePoint web page with IE (internet explorer) and the user presence information does not show.
Find the IE security zone the SharePoint site is in, and turn off "protected mode" for the IE security zone.
Or run IE as administrator
The Office IE add-on loops though all the processes on the computer looking for Lync, so it can use a handle to the process to communicate with it. When IE is enforcing protected mode Windows security restricts the process list that is sent back to the Office IE add-on and the Lync handle is inaccessible.