New test yesterday evening. Everything went smoothly except 3D Dice. For some reason, after two rolls, results were not showing up anymore in the chat window. We finally decided to give up the 3D option. We were using Google+ Hangouts, I was on Imac, OS X and Firefox 17.0.1.
Not a big issue, 3D Dice is nice but we can easily cope without it, as it's more a graphical gadget imho :-)