After Updating from 14w21b to 14w28b.
I had Netherportals in my Netherhub, which weren't lit anymore. Some on both sides some only on one side. After going throug one of these protals i got some pratial lit portals (see screenshot).

I'll try to reproduce it with a word backup for the update to see if this happens again.

Edit:
Found another issue with this "broke" portal. When you're going from the lit portal to an unlit portal, as normal a new portal will be created but unlit and you will be ported to a random spot way up in the sky (40-60 Block above ground) and as result you will fall to death.