Clip+ Loses Albums

After loading music on my Clip+ external memory, I can access it by album, by artist, or by folder and find and play any music I’m looking for. All of the ID3 tags are correct. Then at some random time an hour or a day or a week later, the player goes into Refresh Media mode on its own, and when it’s done, several albums are gone from the album display. Usually, all albums beginning at some arbitrary place in the alphabet, like the middle of the Ts, through the end of the alphabet no longer appear in the Album display. The music is still there, and I can access it via artist or folder, but not via album. I’ve had two Clips+ now, and they’ve both done this.

To recover, I’ve had to recopy the folder(s) containing the missing albums from my PC to the Clip’s 8 GB external memory. Sometimes I’ve had to format the external memory SD card and copy all folders back to it again.

Is this a known problem, or could there be some kind of incompatibility between my Clip+ and the SD memory card?