Me too! I'm on Joomla 2.5.6 by now. Maybe that's the problem?
Anyway, it seems an extra space is added to the absolute path to the icon(s)
So for example:
(where the underscore represents the addes space.
If I remove the space (when I choose 'view image' by using my right mousebutton) the icon does show up. This is only a problem in Firefox as far as I can see.
Is there a solution for this? Help is appreciated.
Thanks for the wonderful extension!