So it's a different problem, I guess--maybe a bug? From an earlier save, wearing the fake rings, I tried moving into the magic barriers, and as before, they remained in place. I made sure I was standing on the floor disks, first. So when that failed, I had the alter destroy the fake rings, had Ahomar cure the resulting Dread Curse, and then joined the Anama, gaining the real rings. Moving into the magic barriers with the real rings fails to remove the barriers, and the stairways remain blocked. I tried all of the barriers, just to be sure. Just wish there was another way to get L3 Divine Fire, as that's the only spell I lacked at the end of the game.
Regards,
Dan