My sansa fuze keeps freezing

Start the sansa updater, set sansa to recovery mode plug into computer. unplug when told sansa should restart (Lock sansa press and hold rec and menu until recovery begins)

Also you can Try
Reset All
NOTE: THIS IS AN ADVANCED OPERATION AND RESTORES ALL SETTINGS
TO THE FACTORY DEFAULTS. NORMAL USERS ARE NOT RECOMMENDED
TO PERFORM THIS OPERATION!
If your device freezes up press the Menu button and hold for 15 seconds.
This is like a power down of the device. Once you perform the reset, the adjustments you made during last operation
will be gone.....