The image at http://www.geocaching.com/profile/?u=Cloak.n.Dagger
works fine for me (using another setup than mac).
First I would suggest that you hard refresh the page, I am not sure about Mac and their browsers, but shfit-refresh is typical for other operating system and browsers.
Then I would try another web browser to see if that helps.
All in all, if it doesn't work, it sounds like an issue with Geocaching.com and not Project-GC actually. There popup question about following the link is fairly new, and I would expect it to be related to that.