Do you have a send on that track to a reverb bus for example? If so, when you pan completely left or right, you'll still hear the reverb send on both channels.

2) Nothing in right speaker.
 
i closed my main project > opened a new one > added one audio track with sample > converted to mono > output master > master output -AS1 stereo > babyface - AS1 mono Hard Left As2 mono Hard Right .
 
Nothing else in the New platinum project > hit play > hard panned Left > only right headphone connected to my ear> very audible sound coming through right headphone  > found this http://forum.cakewalk.com/100-Panning-Issue-m3109378-p2.aspx#3367618 ,didn't help ,though i am absolutely positive i didn't have this problem a month or 2 ago !! i did update the baby face. can i roll back on the babyface ,is it possible?
 
i disconnected the baby face and ran the new project through asio4all /win audio and hard panned either way is silent !
 
can anyone confirm that has a baby face with driver 1089 and hardware revision  223 , that when they hard pan the other speaker is silent ?? or is this a baby face fact .

Do you have a send on that track to a reverb bus for example
 
no i opened a new project to troubleshoot simply! but nothing i do is fixing this problem ,
 

I searched on RME babyface problem pan and there were a lot of hits. Maybe some of the threads apply to your situation?