Half bottle problem

25 Sep 2011: Today, we opened 4 half bottles of white burgundy and 3 were madeirised.  The ones that were madeirised included 1 half bottle of 1999 Chassagne Montrachet Les Chaumées, Ramonet and 2 half bottles of 2002 Chablis Vaillons, William Fèvre.  The only one that turned out ok was the 2004 Meursault Perrières, Bouchard.  This has been more or less our average hit rate with half bottles of white burgundy: around 25% would turn out alright if we're lucky.  We have been luckier with those from more recent vintages.  Not sure if we can draw any conclusion from our experience, whether it's to do with the vintages in question....from 1995/6 to 2002 or it's to do with the bottle format or it's to do with particular winemakers.....I wonder if half bottles would be better off being sealed with screw caps to minimise the risk of premature oxidation???  We have so far not experienced this problem with Sauternes and Barsac, and half bottles are very popular formats with these two appellations.  Something to do with the higher sugar and sulphur content?