To be quite honest with you, I had never succeeded in getting a faction to submit as protectorate until this most recent campaign. I had beaten Gaul back to just it's capital in Celtiberia, and laid siege to it, and they patently refused Protectorate status. I read about the save/load exploit on a forum, and I was absolutely determined to have them become a protectorate even if I had to use an exploit. So I tried it, and it had absolutely no effect. They only finally caved in after the siege had been held for several more years -- for a price, of course.

I ran into the same situation with Spain a few turns later at their capital in Lusitania. They had no other territories and their capital was under siege. Again, the save/load had no effect. However, after a few turns of being besieged $14000 convinced them.

I should have save games of both of these situations as well.