My Cowon S9 doesn't read my mp3 files

[aavichai]

hi everybody
I don't know what to do and who to ask

I hope you will help me

every time I put songs into my mp3 it doesnt show them all
if i connect it to a computer then I can see them
but when I open the MP3 they doesnt show
and if I put a folder, when I try to enter the folder it stucks
and I have to push the reset botton

I have many folders
and all the songs I have on the MP3 is something like 4000

I updates it to 2.53

sometimes when I do a hardisk check on windows it helps, but still for not all the files
so if I put 4000 song on it
i can only see 2500 or something like that

thnk you