I'm fairly sure I have listened to incomplete MP3 files before, and then restarted its download, without it having to start from 0% again, but I can't say I saw the word Preview appended to the front of the MP3 file name, so I'm not sure it's a valid comparison ?
The 55% incomplete file, is a .pdf document.

I too am not a developer, just a user, I hope my posts are ok for this forum ? It's the first forum for Limewire I found.