Had a few problems lately with MP3 filenames when added to the MP3 folder on the HT300 Compact flash card
Always try and name your MP3 files as short as possible and no spaces or special characters.
So ideally something like 'track1.mp3' or 'AveMaria.mp3' etc
Try not to call them 'Ave Maria track from folder.1.mp3' or 'title track/3 box1.mp3'
Once you have mastered the placing of MP3 files onto you machine it is always a good idea to make a copy of the complete card and save to a folder on your PC. That way you have a back up of your MP3's and all your playlists.