My sony ericsson hazel's red button problem?

well i have a problem recently i noticed that the red button on sony ericsson hazel which is for turning on and off the phone and decling calls ans returning to the main menu as all red button does't work when i try to turn on my phone.it turns it off and declines and all stuff but will not turn on the phone so i use my charger to turn it on i instaled the firmware again but nthinbg happened please help