>1)I had set my ISO in the menu setup to be 100: because when >the sun was still in the frame I could shoot at native ISO and >f8 (a sweet spot for the 24-85mm 3/5/4.5 VR) and shutter speed >around 1/250 (because hand holding a 24 MP sensor).
Makes sense to me so far
>2} I had in the menu set my Auto ISO to minimum 100 and >maximum 3200 (because that seems to work out for little >visible noise most times for me).
There isn't a minimum setting for auto iso - it takes the base iso setting that you would have chosen in the menu, or via the iso button or command dials if you are using easy iso.
>3) I also had set "Easy ISO" on in menu (as pointed >out by Brian earlier) and THIS was new to me (did it earlier >that day for 1st time).
Still with you
>4) As sun went well below horizon I used auto ISO (held ISO >button down and used subcommand wheel to enable Auto ISO) and >this worked fine for awhile.
Yup, makes sense.
>5)It was getting pretty dark but the colors were still there >in cirrus clouds swirling about in the west - and AUTO ISO now >would not keep shutter speed above 1/160, so I wanted to >"manually" dial in ISO - I could not, the ISO button >did not operate as I had expected - because I had enable the >"easy ISO" function.
This isn't working the way it is supposed to. Easy iso should not disable the iso button.
>THIS is when I noticed what I described in OP. Now I know why, >and I am OK with this - I was just surprised. Now the command >wheel changed ISO without pushing the ISO button.
Yep, that's the easy iso bit.
>When I went back to menu ISO settings I saw that the camera >had now selected AUTO ISO to be "OFF" (I had set it >to "ON" earlier) and the ISO value selected was now >3200, the highest value selected when in Auto ISO, when I had >set it to 100. Also weird for me, but I now understand this. >Just had to reset for the next shoot.
This is the part that worries me (for you at least) and there are really only two viable choices that I can see:
1) You accidentally changed base iso with the command dials / possibly the iso button (but you said previously that yours doesn't work when easy iso is set to on) and also accidentally turned auto iso off as well. 2) Your camera isn't functioning properly and you should consider contacting either the store that you bought it from, or Nikon support. Secret option 3) did you change to or from one of the "U" modes? If these are setup differently (i.e. with base iso to 3200 and auto iso to off) then this would explain it.
Sorry to hear you're having problems, but I'd rather work through this with you than have you using work arounds that you shouldn't have to!