Thanks, the problem was Windows Firewall.

I can run a slideshow on the Juicebox Flickr demo page perfectly by entering...
User Name: mintusmaximus
Tag: BBB 2002 - 2006

...but my installed Juicebox Builder refuses to accept these, spitting back the error message "Gallery Load Error Flickr User Not Found".

Any ideas why this is happening?
(I can create a gallery from local files OK)


Thanks
Kevin