CD reading error

Hello, I have CDs i have burned with mp3 files. About half of the files can be read without problems. However, the rest half can not be read due to “file not found” The files appear to be on the CD and I confirmed that by looking at their properties. All the files are complete and If my memories serves me right, at one point these files used to open with out problems. I am very confused with this problem. Please HELP!
A digital slick