One of the upgrade paths from ver1 to ver2 was to import the products from ver1 to ver2. All that then needed to change was possibly the link on your site needed it's product number updating. Was assured by 2CO that this works fine.
Well....not anymore it does not. Of course there are no annoncments to this because we are talking 2CO here.
So if you upgraded and imported your products you would have had many failed orders this weekend.