Well it did not make any difference in the end, still had issues but have now found the cause for certain. It turns out my motherboard does not like having 4GB of my OCZ PC2-6400 RAM, indeed it is not even listed as compatible with my board. So after some advice on the ASUS forums I took 1 2GB stick out and it has been just perfect for the last few days. So now only have 2GB RAM but never needed 4GB anyway.
