The fact that it works OK on your son’s Clip+ but not yours may indeed indicate a defective player. Just to be sure though, you do have it inserted correctly so it’s locked in, right? You should hear 2 faint clicks as it locks into place and the edge of the card should be more or less flush with the player’s casing.
Is the player less than a year old (2 years in Europe)? If so, SanDisk is very good about replacing defective units under their warranty.
