Try checking the connections under the seat - if these (not very good) connectors are faulty, the light can flash as you are driving. Changing the seat position pulls on these wires and causes this common problem. Make sure that you have the ignition off as a minimum (since you are dealing with a safety system - airbag) - ideally, you should disconnect the battery, but beware of losing the radio code etc.
DaveB, July 2007