Problem with FinePix S4000
I agree with Paul. Either the 'Back' button is stuck down or the switching mechanism of the 'Back' button is broken. Seems to be the most probable causes...
You can call Fuji to try to get a repair cost out of them... or ask if covered under warrantee... more than likely, however, the cost of repair would be about the same as buying a new camera. You won't know for sure unless you call them.
Patrick : )