I had the same problem and I decided to try the wma files instead. I really like the way the phone interacts with the wma files you can search and sort and do all the things that you do with your music when it is on the computer. Also if you have them in mp3 format look for the post with the free mp3 to wma conversion it was quick and easy to use.
I just got my microSD card and music essentials kit for my vx8300, but I'm having trouble playing mp3s on it. I already enabled MP3 through the secret code, and I know if I use Win Media Player then they will be converted to wma.
I don't have a card reader, so what I tried doing was using the USB cord to copy/paste them onto my phone in the music folder. Problem is the phone can't read them when I do that, and for some reason deletes them.
Any suggestions? Do I have to have a card reader to transfer the MP3 from my pc to the phone then plug the card into the phone to play MP3s?