It may be that your music library database has been corrupted. There are a few things you can try though. Connect the phone to your computer and open Nokia Suite, then copy/sync your music library on the phone again.
If the problem persists, you can try to reset your phone settings by dialling *#7780# followed by security code 12345 (unless you have changed it). This does not remove any personal data, but it's a good idea to back up your phone with Nokia Suite just in case.
Let us know if this helps,
Hi, I also experienced the same problem.. Sadly I've done the tips above, but still didn't work. The files cannot be read in the Music player. I also have tried other tips (googled) and I cannot find "private" folder in my C7 device..