Since the King Krogmos update (actually I think it may have been the first patch afterwards) the Auction House's sort menu is now drawn behind the main window. There's just enough showing on the right hand side that it's still "useable" but you can't read it and is obviously broken. I've restarted the game a few times and received at least one other patch since I first noticed it but none of those fixed the problem so I'm pretty sure this is a code problem.

Update: This now appears to have fixed itself on my machine. Sorry for the confusion.