Often you can stop a frozen Fuze by holding up the power button for a long time–15-30 seconds and keep holding it a while after the screen goes black. That is called a soft reset–turns it all the way off, like rebooting your computer.
It wouldn’t hurt to reinstall or update the firmware. Use the manual method–you don’t need the Updater, since in all likelihood the Fuze has gotten its final firmware.
http://forums.sandisk.com/t5/Fuze/Sansa-Fuze-Firmware-Update-01-02-31-amp-02-03-33/td-p/139175
