1) Insert an otherwise known-good (e.g., you know it can be read in another BB) media card into your BB and see what happens.
2) Insert your media card into an otherwise known-good and identical BB...see what happens.
3) Insert your media card into a PC card reader...see what happens.
The result will indicate if your media card or your BB is bad. If it's your BB and you have warranty, then seek warranty evaluation from your original place of purchase.
Occam's Razor nearly always applies when troubleshooting technology issues!
New to the Community? click here and also here. Please click here for helpful information to guide you as you proceed. I always recommend that you treat your BlackBerry like any other computing device, including using a regular backup schedule...click here for an article with instructions. If anyone has been helpful to you, please show your appreciation by clicking the button.