when you modify something media (music, ringtones, pictures, videos) in either memory (device memory or media memory), the blackBerry device will create an index file so that those files can be seen by the Media Application.
it's a bit like the thumb.dat files in Windows.
That index file is named BBThumbs.dat . There is one such index file in every folder that contains a media file.
Without that file, the Media Manager sees not media file, but the Media Explorer does (because it's basically a file browser).
when you copy files using the mass storage mode, sometimes the index file does not get updated. So you have a file, that you can see with the Media Explorer, but not with the Media Application.
there is a solution : delete the index file, and have the device recreate it. There are two ways to do it :
1) use Windows explorer, show the hidden & system files, and delete those BBThumbs.dat files 2) remove the media card and insert it once more.
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