only the apple logo comes on the screen

hi there!!!
i am using iphone 3g n i jail broke it a month ago,now i am having problem...is like,the phone suddenly got hang n when i switched on the phone,only the apple logo comes on the screen....
i tried pressing both home and turn off button,even then its not working...
So,PLEASE HELP ME!!!!!!

Restore it back to factory firmware.

its nt detected in the itunes so any other thngs dan that, plz thank you

Have you tried shutting it completely off or doing a reset using the power and home button?