I have an RCA Lyra, and I was able to get some music on it, and now all the sudden, when I plug it into my computer's USB port, it doesn't come up on the computer, normally it shows what drive it's in. I also have a memory card in it, I don't think it could be full already. I only have 51 songs downnloaded onto my Lyra, can anyone help me figure out what's going on?