By "to the letter", do you mean that you formatted the card in the radio?
What's the capacity of the SD card? Some radios don't like large capacity cards. I'd stick with something like an 8 GB card even though the owners manual says the radio can work with up to 32 GB cards.
In order to avoid problems with files getting corrupted during mid-write or mid-read, I'd only insert or remove a card with the radio's power turned off.