Hi,

Just checking back and thanks for the replies. I've pretty much done what has been suggested other than the ROM upgrade. Fan is fine, ventilation is fine so I suspect no heating issues in that regard.

I fear that if I reflash the roms and it freezes during the update it will likely screw it all together, maybe worth a try though. Since my last (first) post I've sourced another CPU but with the same results. I will try the prism card in another slot and report back. Otherwise its:

A) A Nucore upgrade - how much are they at PSPA..?
B) Anyone have a replacement motherboard to suit..?  I've suspected the MB from the get-go and tried everything else, but all points to the MB.  

Thanks.