>Yes - I think the problem here is that Lock Mirror Up is not
>available when a particular value has been chosen for one
>Custom Setting, so the fix is to select a Custom Setting bank
>where that value has not been selected.
>
>My point is that selecting Bank D would only be a fix if that
>Custom Setting (whatever it may be) is still set to its
>original value.
>
>I have read elsewhere that Custom Setting g4 may be a possible
>culprit, but as I don't have a D800 I can't check it myself.

Thank you Brian,

For a guy that doesn't even own the D800, my hat's off to you! You did indeed identify the true culprit.

I screwed around with that g4 setting and discovered that when I assign the shutter button to 'Record movies' the greying out problem occurs but when I assign it to Take photos, the problem disappears. The g4 has to be assigned to 'Take photos' in each Custom Menu bank to prevent the graying-out from occurring in that bank only. Apparently I accidentally had g4 set to Take photos in Custom Menu bank D and because the Nikon tech had me switch to that bank, the problem seemed to resolve itself.

I found a reference on page 374 in the manual to the greying out for image dust off ref photos when g4 is assigned to record movies. There are references to other menu items that also won't function if the release button is assigned to the 'Take movie' role, but they apparently forgot to include the mirror lock up for cleaning feature in this section.

I'm contacting Nikon again on Monday. Boy did they hand me a load of #### with that D bank explanation. What a bunch of clowns.
I'm also e-mailing David Busch to let him know what the real fix is since he also thought it had something to do with his wireless transmitter and that Custom Menu bank D hadn't been altered on his camera.