Seems whiskies can and do change between bottlings, and it always hurts if it's for the worse, and a personal favourite...or in the case of Ardbeg 10, a staple!
The last but one Lagavulin 16 i bought, was in an old mouldy box from an Indian deli in the shepherds bush Rd, at the "old " price of £29. It had almost no nose( compared to how I'd grown to love it) and was sweeter than usual. Still tasty. The last one, my mother procured for£18(!!) at "Cash and carry", and this was a little weak, a little bitter. JM reckons the 2006 batch was "back to its usual self..." so this probably was from the previous batch.(hence the price??)
the last Ardbeg 10 I opened at the beginning of last month, and I must say my reaction was not unlike our friend "adogranonthepitch." I thought "sh*t! I just bought 2 litres of this from duty free!"( For only £45 i might add...) but now the bottle has been open awhile it seems closer to its old self. Maybe Ardbeg reacts with air more than many...
I recently played in a bar that actually had an Ardbeg 10! The bottle had been open a while, I guess, and probably not visited that often in that cradle of culture that is rural Kent, but it was unusually sweet!
Try yours again in a day or three...and maybe after a "palate cleanser" of something cheap and nasty. It's bound to taste better!