Are WAVs under 4KHz deliberately played silent?

[sheddy]

Have some WAVs I'm working on for an old 8-bit computer which can't support high bit rate sample playback, and noticed that if they are saved at a bit-rate of under 4000Hz VLC 1.1.5 doesn't produce any sound when it tries to play them. From 4000Hz onwards they seem to work fine. Just wondering if this is a deliberate quality threshold cut-off or something? Other media players on my system play them OK (Windows XP SP3, Media Player 11). I assume this would not be OS specific, but if it is, sorry for posting in the wrong area.