The corresponding line in BSplayer.USER_NAME.xml file is the loooong one starting with
<Keys type="kbin">
and ending with
</Keys>
To do this you can also use my program
BSP Definitions Manager, and choose to "Blank all definitions in BSplayer".
Give it a try and let me know
(maybe you can also try to use the BSplayer button "Reset to default" present in the Preferences section "WinLIRC and key definitions")