Its a security thing if the light by the hazzard button flashes rapidly when you try to start it.
But don't rule out the battery too quickly. Sometimes accesories will operate, but the battery could lack the amps to turn the starter. See if it takes a jump. If it doesn't, it could be the relay on the starter, which means the starter would need to be replaced. Or if its a manual, double check the clutch interlock.