I wonder if anyone can explain this to me. Last night I opened a 05' Bordeaux, and yes I know its infanticide, however I have a bunch and was itching to try this one.

Basically, i opened the bottle and tasted and was very impressed, very lush dark fruit and chocolate, smooth tannins, nice finish etc etc. Anyways, as it sat in the decanter the nose and taste seemed to dissipate and almost shut down? Is this possible? I thought wines tend to open with air? Any thoughts? Thanks---Marc

definitely does, there's some mumble jumbo behind it, but I find that with a few of the 03 bordeauxs too.

no idea why

It may be easier to answer this question when we know which wine we are talking about.

Some wines tend to shut up after a while and then open up again at their own discretion.

But most 05' bordeaux are very open, fruity wines that are pleasing from the beginning. No dead children there.

I opened a 2003 La Reserve de Leoville Barton, 2nd wine of leoville barton, and had similar experience. we had it in a restaurant. the waiter uncorked it like 10ft away we could still smell the rich aroma, it was decanted in a regualr decanter. at first it tasted and had the nose of a solid cru classe , but after 45mins in the decanter it started to turn dull. the flavor was going away and the nose was getting more intense with the sense of alcohol.
i waited another 45mins and the wine did not turn into anything better. is it possible that it was part of the long transformation into its full potential ? or this 2nd wine doesnt seem to hold longer period of breathing ?

Thats the way wines from certain vintages and regions roll. I had the 03, 04 and 05 Pegau Cdp on release and they all showed well after decanting but I know they will shut down at some point. When I recieved my 03 Bordeaux I opened a Giscours and it was real fresh with good fruit and tannins but after an hour it started to fade. If I buy multiple bottles of a wine I'll try one and then depending on my evaluation of how the wine tastes now and will evolve over time I might just have to be patient.