While your sentence sounds better in English, it actually has a slightly different meaning: it does not combine the boy and the girl into one entity. The Russian translation of your sentence is:
Ни у мальчика, ни у девочки нет хлеба.
Yes, this question is fiendishly frustrating. I think it must be some kind of glit h in the software. Try typing in one of the sentences Zircul, above, says is accepted. When that doesn't work, send him a screen shot. Maybe he can figure it out.