First I have heard of a CB actually tripping. Every report I have ever read said that although the L/E flaps were seleceted down, the pneumatic system that powered them wasnt switched on due to the CB not being set, and that the L/E devices were not included in the configuration warning at that time. There is some suggestion that the aural T/O config warning was a MEL item and a recommendation was that it should not be (not that it would have made any difference in this case if the L/E flap setting wasnt included in the warning parameters)
In 1974 the following appeared in Flight International: "Flight has investigated the configuration on a 747 simulator and finds that a combination of pneumatic bleed-valve selections and circuit-breaker malfunctions can produce a situation where the pilots' caption warning shows green, but only four of the eight lights at the
engineer's station agree. The other four lights are extinguished by the faulty circuit-breaker setting"
The regrettable thing was that the same thing had happened the year before to BA (thankfully without incident) who had communicated the incident and several airlines were in the process of ordering mods as a result. After the Nairobi crash there was a debate as to why some operators, but not others, were aware of the issue.