backup not working

ok ill try keep this simple. all tracks are on external hard drive 1. i bought a new external hard drive and have backed up all my tracks to this. i have also clicked and dragged all my playlists from hard drive 1 into playlists on hard drive 2. now it seems when i open hard drive 2, all my tracks are there....wave forms, playlists. i can click on them and listen to them. but when i drag a track to the player at the bottom of the screen it simply won't load. its like its frozen. and to add it was working ok last week although a little slow. when i click eject the drive it says its in use? if i plug hard drive 1 in i can click and drag tunes no problem. I've downloaded the latest updates and firmware.