MP3 player suddenly not connecting

Two nights ago, I added some songs onto my mp3 player and it was working fine. Yesterday night, I try to connect it, but the computer isn't detecting it. To make matters worse, my mp3 player says it has established a connection, and it works fine when it is not plugged into the computer...I am so frustrated!!!! I have a Coby 20GB MP3 player, with 1,744 songs that I can't upload onto my laptop now!!!!!!