Since there is no update yet for Auctioneer that I know, I started to use Auctionator instead since 4.0.1. There seems to be a new function/rule that mass posting with a single click is no longer possible, each posting requires a confirmation. I'm pretty active on the AH as it's one of the game aspects I enjoy most. With a couple of 100 auctions going on all the time, dragging and clicking would take quite a while. To make that process easier I made a simple macro to click the confirmation box.

1) Drag whatever to the 'Sell' tab so that the 'Create Auction' button becomes visible/active.
2) Put your mouse pointer on top of the button.
3) Enter in your command line (chat box): /run print(GetMouseFocus():GetName())
4) This should give you the name of the UI element you are currently mousing over. It appears in your chat screen. For this particular case it is 'Atr_CreateAuctionButton'
5) Make a macro /click Atr_CreateAuctionButton and drag it to your actionbar. I have it on 1.

So what I do: open bags + auction window. Alt+right click the item you want to auction, it will automatically appear in the auction window, and then I hit 1. Done. This is much faster than clicking, dragging and confirming a ton of auctions. Obviously I've configured my stack size and undercut price beforehand.

While most ppl will know this, I figured it might be helpful to post it for the others. Obviously this should work for other auction tools as well where you have to mouse click to confirm.