I am experiencing the same thing on http://demo.silverstripe.com/flickr/.

I did have this working on my site running 2.2.3 and I managed to get it working correctly. But now I have updated to 2.3 RC2 I keep getting java errors associated with the light window and when I click on the image or link nothing happens. I am now running the latest daily build of both flicker and youtube

The errors I get are In fire fox
"Error: Prototype.Browser has no properties
Source File: http://site/~sstest/youtubeservice/javascript/lightwindow.js?m=1229778348
Line: 1003"

and in IE
Line: 1579
Char: 4
Error: 'null' is null or not an object
Code: 0

This same problem effects both the flicker gallery and youtube

I sorted this yesterday, what is happening with the new Requirements includes is that an older version of prototype is being included after the original prototype file therefore cancelling out the newer version to get round this i had to include the files manually at the bottom of my Page.ss and it works fine

Ok i could be wrong here but one problem i had was when i extracted the rar file and uploaded it, the folder was called somthing like flickrservice-v0.2, when i looked at the scripts they were all looking for a folder just called flickrservice, once i renamed the folder the pop up worked.

Mick

that was 2.2.3 haven't played with 2.3 yet might have a look tonight and see if i get any probs.