Dock Notifications Displaying Odd Red Icons Instead
This looks like it might be a problem with a system font.  Try this...


Open Font Book (in /Applications)
Select the "All Fonts" collection in the left-hand pane
Click any font in the right-hand pane to focus that pane
Select all the fonts using Edit -> Select All or Cmd+A
In the File menu, click "Validate Fonts"


If any fonts are corrupt, this method should alert you to the problem.