Seems the AdobeFlash player (or TVNZ's embedded BrightCove content controller) now requires the old HAL libraries to operate it's DRM.
From askubutu http://askubuntu.com/questions/362259/how-to-watch-videos-in-amazon-prime-instant-video
sudo add-apt-repository ppa:mjblenner/ppa-halsudo apt-get update
sudo apt-get install hal
The following extra packages will be installed:
hal-info libhal-storage1 libhal1
The following NEW packages will be installed:
hal hal-info libhal-storage1 libhal1
This now makes it work in Firefox on 14.04.