I'd vote for bad shipping/storage, that sounds really cooked to me.
I don't remember having the 2005 Meursault, but the Bourgogne was
quite solid, and I'd be shocked if the Meursault didn't hold up. And 2
bottles with bad seals under screwcap sound really off the charts
unlikely, reduction maybe, but oxidation? Sounds to me like these
wines got hot. Too bad someone is giving them as samples!
I had the 2005 Mersault and it was fine as well and still have a bottle
left of three. Sounds cooked to me.
I re-sealed one of the bottles and tasted again this morning. The
color is clear and still light golden but the nose is still very ripe/
oxidized apples and the wine is very bitter and astringent on the
palate leaving the impression that one get's after gargling with
hydrogen peroxide. Must have been cooked somewhere along the line.
Pity.