Air Bag Deactivation Switch Problems

Does anyone know why the passenger air bag deactivation switch suddenly turns itself from off to on. This morning on my 1999 f250 SD the air bag off light was not lit and the air bag icon on the dash panel is lit and stays lit. I put the ignition key in and turn the switch to off and it will not disable the air bag. The owners guide says have switch serviced at dealership immediately. My concern is, can this cause the air bags to deploy? If so, is there a way to deactivate the air bags until I can have the switch serviced? Thanks to anyone who can help.