I've had this happen also and fixed it by doing the following.
http://www.taperssection.com/index.php?board=14;action=display;threadid=16338It's probably a good idea to do a Format All regularly to ensure you don't run into problems like excessive fragmentation. Instructions:
1. Remove the battery or press the reset button.
2. Either while reinserting the battery or after reset ensure that the stop button is held down.
3. As soon as the 'Creative' logo appears on the screen during the boot sequence, release the stop button. Immediately press and release the play button. The unit should boot to a diagnostics mode with several recovery options.
Those are:
[b.] Format All (*WARNING* ALL contents will be lost, including pre-installed content)
Good luck and let us know how it turns out.