It looks like its because he didn't finish his move. He pushed his pawn forward, clicked MOVE, but then did not select which piece he wants... so, he's in the middle of his move still.. it hasn't been completed (which, you can also tell because there is a pawn on the back row.. something which can't happen).
I wonder what he (white) sees when he logs onto the board.
I made this mistake myself not too long after I joined the site.
I pushed a pawn on to the back rank and clicked move, but didn't notice that the piece selection option came up in the right side window. I went back to 'My games' screen and kept moving in all the rest o my games. Took me a little bit to figure out why it said it was still my move....
Sounds like this guy did the same thing. Just PM him and let him know that he needs to pick a promotion selection in the right hand window.