I had that issue while on the quest where you get drunk with the guy in the tavern
Spoiler and you wake up in some temple. (you pick some of the bottles up when cleaning the mess you made in the temple)
If your on that quests, the wine will be sellable again once you've completed the questchain. No worries.
You're right, it was that quest chain! Yay. Only needed 2 bottles to be picked up on that quest, but every subsequent bottle I picked up elsewhere was counted as a quest item, even though it was not needed. Bit of a bug there methinks, but I completed the quest, and now I was able to sell off all the excess wine. Thanks very muchly.