`.TXT` file association to Notepad++ "stopped working"

Question

I recently formatted and then reinstalled everything, but oddly now, Windows 7 refuses to let me set Notepad++ as the default .TXT editor.

I try to set the "open with" file as usual:

• right click a .TXT file
• Open With... → Choose Default → Browse
• paste "C:\Program Files (x86)\Notepad++\notepad++.exe"

... but Notepad++ doesn't show up in the dialog (image below), and the file instead opens with lame old Notepad.exe.

However when I open "C:\Program Files (x86)\Notepad++\notepad++.exe" from the ![Windows Key][oldwinlogo]+R Run dialog, Notepad++ opens without a problem.

Also, certain files' context menu have Edit with Notepad++, which also works fine.

From my registry, in case it's relevant:

[HKEY_CLASSES_ROOT\.txt]
  Default="txtfile"
  Content Type="text/plain"
  PerceivedType="text"

[HKEY_CLASSES_ROOT\.txt\PersistentHandler]
  @="{5e941d80-bf96-11cd-b579-08002b30bfeb}"

[HKEY_CLASSES_ROOT\.txt\ShellNew]
  ItemName="@%SystemRoot%\system32\notepad.exe,-470"  
  NullFile=""

I tried rebooting... Any ideas?

Edit: I had also tried the editing the Associations directly in NPP as admin, without success. Note that I'm using Windows 7.

(I just got all my N++ setting/themes/plugins/ftp/etc all painstakingly setup, and it was working fine until I tried it this morning, so I'm hoping for a fix other than reinstalling N++.)