Yet another question for FOODIE.

[Thomas]

If you've got vinegar going you can't do much to stop it now.

Did you add SO2 before fermentation? I would have done so, to protect against quick oxidation. You also need to check SO2 levels about a week after having added them, to be sure that you had added enough, especially in sweet wines.

Sweet grapes have already been oxidized some on the vine, so the juice needs careful handling and usually a higher concentration of SO2 than regular whites.