First step is a trip to the website, at www.creative.com. You'll find a handy Recovery Tool and update downloads.
If these things fail, see if there's something else on the website that might help. If not, contact customer service. They were prompt in replying to my email when I had a problem.
Last week my mp3 player appeared to have died! While listening to it, I turned my mobile phone on and while waiting for the phone signal, placed the phone on top of the mp3 player. When I got a signal from the phone the mp3 player just stopped at exactly the same time (as the signal arrived). I checked it and noted that it was shutting down. However it didn't actually shut down completely and appeared to be stuck (I was unable to turn it off). I assumed that it was just a case of resetting. I reset the player but after completion, the "rebuilding" message was still on the screen even though there was nothing happening inside the mp3 player. It was impossible to turn the player off and it eventually did so once the battery ran out. I then connected the player to the mains; it then "rebuilds" but once again becomes stuck once the rebuild has been completed ("rebuilding" remains on the screen even though the action has been completed). When I disconnect the player from the mains after the "rebuilding" is complete, it is completely dead.