I have just been volunteered to download some music on to a friends iitronics 512k player, an dmet the same problem. It seems that if you download single tracks, each one becomes a new folder, and only 99 are allowed. So you have to put tracks you want into separate folders (to a maximum of 99 in each folder). Then click and drag the completed folders separately across to your iitronics. Worked on my friends!!! Good luck.
David Ross
June 2008