Hi – I know this is 5 months old and you’ve probably moved on, but this is a javascript bug and can be managed if you make sure at least 1 radio button is selected on the “Viewer Size” sizes – even if you’re not using the viewer.
This happens if the default viewer size isn’t available, the plugin won’t preselect a size and therefore “viewer size” is undefined and javaScript aborts the insert.
A bug, yes. But for me it was worth fixing/working around because this flickr plug-in seems to work the best for my needs, bugs and all.