Unformatted disk

Hi, This month we bought 2 sansa shakers for our sons. Today it was the fists day they used them. I copied some mp3’s to the SD disk and everyting worked fine.

Suddenly one shaker stopped playing. When i inserd the disk in my laptop i got the message that the disk was not formatted. A few hours i had the same problem with the other one.

does somehad the same problems?

Kind regards