I click "Save As" one day in my favourite application only to be very confused:

Ahem, where do I enter the filename?? Which folder is empty?! Let's try clicking the "Browse Folders" button:

OK, now my folder is not empty but still nowhere to change folder or enter the filename.

One last try, let's click the "Hide Folders" button:
Now, this was in Mozilla Firefox. So who's to blame, Firefox or Vista? It is a standard dialog provided by Windows so it would be odd for Firefox to cause this. However it was not occurring in other applications at the time and trying again to save a file in Firefox resulted in the same mess. Even the breadcrumb/navigation bar was missing! Maybe OLE/COM initialisation related, who knows...