Adding to my own reply--
I did what was listed here, in that I added the income numbers from lines 1 and 2a to get my total income. Then subtracted the foreign income number I had been given in order to get my US income amount. Added the Total Income and US income numbers in box 14 where applicable, et voilà(!) no more errors.
Does not incite a lot of confidence in the tax preparers that my Trust account officers used, but at least it seems to be good now.
