Steps to recreate:

  1. File->New
  2. Click the 'Combo Flags' icon in bottom-left Screen Panel; the 'Select Combo Flag' window appears
  3. Click the dark blue label search box immediately above the OK, Help, and Cancel buttons
  4. Try to type the name of a combo flag; see how nothing happens
  5. Click the combo flag list box with the scrollbar
  6. Now you can type the name of a combo flag