Thank you for that information.
Initially I used dimensions given on the manufacturers' websites for the hubs and the rims.
However, I physically measured and verified the hub dimensions before ordering spokes.
I did NOT verify the rim ERD, choosing to rely on the manufacturer's information as well as that
provided by Peter White on his website. And, as I have used this rim in earlier builds without incident,
I chose to use Velocity's number. If that is the error, then my apologies to Machinehead Software and everyone else.
If the rim is that much larger, I will probably not get a tire on it!
But, that still would not explain the differences among spoke length calculator programs.
Of the several I have tried, the majority seem to hit on or around a number 1mm longer (give or take) than Wheelcalc's figure,
but shorter than that derived using Pro Wheel Builder's program.

I have rechecked the build of the front wheel, and have verified the number of crosses (errors in that regard would result in a non-buildable wheel,as spoke length deltas required for alternate # of crosses are far greater than 2-3mm) and I have verified that the stagger pattern between hub flanges has been correctly laced.
I am not above making mistakes,nor admitting to them as I have made many. But the lacing of this wheel is not one of them.

Dunno.