When you defined these keys you probably also checked (selected) the box "Global key" ??
In BS.Players "Key definitions & WinLIRC" (if applicable for both [Windowed mode] and [Full screen mode]) select the functions you (re)defined and then click on the button "Reset to default" (at bottom right).
When (re)defining again maybe don't (also) check the "Global key"-box.
You can easily see that the functions selected are the ones you (re)defined as the keys used by you when you (re)defined will be displayed in the right hand column of BS.Player's window, below "Assigned key/mouse button"