On my new webshop I sold two items - in both cases the stock-counter did not change.
Since I sell single artworks, it's pretty important that I don't double-sell. ( http://www.oxpal.com/shop )
Both these were paid via paypal, maybe that's the issue? An earlier sell went fine.
I did get confirmation emails for the sale. Though the second took soo long that already before I've changed the item's status. But I assume status should change instantly- there wouldn't be a delay, right?
There is a user with the same problem it seems (just his post is not here in the WooCommerce section, so I guess the support won't see it: http://wordpress.org/support/topic/woocommerce-stock-problems )
(Current version of WooCommerce and WordPress. Personal theme. For each item I check "Enable stock management at product level" and "Enable this to only allow one of this item to be bought in a single order" - and set the quantity to 1)