Why does my movie player not reset?


I have a WebMoviePlayer which I modify with this code:

“s” is set according to the selection in a WebListBox. This works the first time my app runs, so I know “s” is valid (any row can be selected for the first time).
If I then select a second row, the code above is indeed called, but the movie doesn’t update (nothing changes, the current movie keeps playing).
What am I missing?