I have Sony Walkman 8GB MP3 player (MTP), normally I use Rhythmbox to transfer songs to it, this has always worked in the past. Recently I switched to Linux Mint Debian Edition (for a number of reasons), and today when I went to add a few songs, I remebered having troubles with it copying large numbers of dupliates, so I removed all the songs from it and attemped to copy my library back to the device through drag 'n' drop, when I released the mouse button Rhythmbox quit, tried several more times all with the same results.

Laptop: Acer Extensa 4420
OS: Linux Mint Debian Edition
Rhythmbox 0.12.8
All updates installed

How about just copying the files from device to device? For example, open up the folder you want to copy from, plug in your mp3 player, wait a few seconds for the folder to open. The drag and drop between windows.

Or is your MP3 player like an Apple IPOD, where you need the Itunes software or some other unnecessary middle-man?

I can transfer the songs (and for that matter any other file) but the MP3 player needs to have the database updated in order to play them, which make transfering the songs via that method rather useless.