SD memory partly accessed

Hi,

MP3 player has a flash memory of 256MB. Using only this flash memory, I can load about 120 songs.  When I add a 1 GB SD memory card, the Lyra "sees" only about 180 songs.  This is about half again of the 256MB memory, where it should be about four times as many.

When I view the SD memory card with a computer - it is "full" and contains about 600 songs.  Yet the Lyra does not register them.

What's wrong?  What is the handling?

Thank you.

Mike