This problem has been bugging me for months – when I try to Open or Save As in Windows 7 , I can’t sort the list of files using the column headers. If I click on any header, nothing happens, no error message either. Today, I found this post on a web board:

Sure enough, after a bit of clicking on the little dropdown arrows next to the header titles, I was able to sort the files normally again. Specifically, I changed it to use a date range (today) to filter the list, then removed that filter again. Phew! Many thanks to that poster (Imperfect1).

Updated 18/11: So the problem recurred the next time I used the dialog box. If I clicked on the little arrow, I noticed it says “computing filters”. If I wait until it stops saying that, sorting etc starts working again. If I can work out how to get it to stop (or speed up) “computing filters”, I’ll update this post again.