The flash is operated by an electro magnetic solenoid switch which works faster than a mechanical device.
This switch releases the flash head which is spring loaded. Sounds like your spring has come loose and will need to be located back. When the flash pops up normally it activates a micro switch which makes a circuit for the flash to work. Unfortunately you will have to strip the camera down to locate the spring inside the top of the camera.
Dave - camera repairs
May 2010