I have the same problem. It froze when after saying rebuilding library yesterday, then stopped working completely apart from the blue light when its plugged in or the power button is held. There is still a noise when I plug headphones in, but no music is played. I've had it plugged into the computer for a while, and it first said STMP3600 device found, and it isnt recognised by Zen Media Explorer. So I downloaded the driver for STMP3600 and now nothing comes up when I plug it in. I've tried taking it apart and short circuiting it, resetting it and all that, but nothing works.
Any help would be much appreciated.