There seems to be a problem with the JS pop-ups in 2.0.4.
If I insert a thumbnail sized image, then you get a large pop-up as expected.
However if I insert a medium sized image into the post, then you get just a medium image in the pop-up.
The image viewer is set on by default, and to show a "Large" image, both Lightbox and Highslide exhibit the same problem.
The HTML inserted into the page seems correct as you can reproduce the problem just by removing the "_t" from the filename in the thumbnail code to get the medium image/medium pop-up problem.
Demonstration http://www.lifeinthebuslane.com/demonstration-of-flickr-manager-204-problem/
There also seems to be an issue with it sometimes not inserting an image into the post once you've changed the size of image to insert. Sometimes it works, sometimes it doesn't, however I've not been able to work out why, it's seemingly random.