jellalit, It sounds like you may have a hacked player. Your chips true size may only be 128MB but it has been hacked to read as 256MB. With these chips when you add files above the chips true size the files become corrupted and will not play.
You can check like it with the MP3 Player Disk Tool which is part of MP3 Player Utilities.
http://www.mympxplayer.org/feedback-...rs-vt2828.html
To fix the corruption you need to remove the hack from the memory chip like this.
http://www.mympxplayer.org/how-to-re...ck-vt2400.html
Regarding the radio function not all players have the radio chip installed.