It appears that this problem may have been caused by the Network Controller:
nVidia MCP61, as I installed another Network Card and I can now browse the Internet (and after re-installing opensolaris).
To evidence that it was the nVidia card I switched back to this card again and attempted to access the internet, however this failed, so I have now switched back to the card that works.

Maybe nVidia need to look at their drivers for this card.