Could be bad burns (which could be the media, the burner, the firmware, etc). Could be a picky player. Several possible causes. Download Nero CD-DVD Speed, insert one of the discs in your drive, and click on the 'media info' tab and tell us what the media code is, it will be something like 'RITEK G05', 'YUDEN T03', etc. Also tell us what your burner model and firmware is, and what burn speed you're using for your discs.