After a tedious bit of experimentation (burning at different speeds, stopping other activity on the box, and burning on a different box), I seem to have discovered what others already know. Using blank DVDs labeled “DVD-R 4x UI-Tran” that have on the disk the manufacturer ID “ONIDTECH” – all the burned DVDs have errors. Did not know the quality of blank DVDs varied so much.
After wasting more hours than I care to admit, ordered Taiyo Yuden DVD-R Media off Amazon. Apparently Taiyo Yuden is known for the best possible quality.
So the failed Solaris and Fedora installs may simply be due to bad DVDs.