Won't Let Me Transfer Wav Files/Samples

Hows it going everybody. Well I was in the process of making a beat when I wanted to add some more samples. I went to Mode+Load+USB...... but nothing happened. Tried it again.... nothing happened. So I saved all my work (successfully saved). Turned off my MPC, then turned it back on, loaded my Program&Sequence(Beat). Tried to transfer some more samples to the MPC... Mode+Load+USB... nothing happened again!! What's the deal? I've never had this problem.(Every time I connect my MPC to my PC, I always 'safely remove device'). So I don't know what to do. I can't add any more sounds to my MPC. Any help would be great. Thanks. (MPC 1000, JJ OS .3.08)

Nevermind, I figured it out. I went to Office Depot & bought an adapter for my memory card. It's actually better than using the USB Cable for my MPC. Just simply copy & paste, then insert the card in the MPC. Works fine.