Keith,
Thanks so much. Cool web page. I think I'll take some photos of the neck again and maybe that will help. The alan wrench I was using was troublesome and a pain -- it's part of a set that doesn't really fit in the short space between the neck and first pickup, so I'm not really making precise movements, but when I did manage to get it in there, there was definitely resistance.
The nut seems ok. The twist I'm describing is a subtle effect...like the next slowly, almost imperceptibly, starting to corkscrew...it's so slight, it may be nothing, but it does become visible to me near the top of the neck.