ITS FIXED!
I have changed out the Corsair CMX4GX3M2A1600C9 memory to G.skill F£-10666CL8D-4GBRM, and it works! This is the first time I have been able to 'Load Optimized Defaults' and have the machine work correctly with the memory at 1333MHz. It has run Prime95 for 7 hours on 4 threads with no errors and passed the OCCT tests.
It is interesting to note that Memtest found no errors with the old memory at any speed, even when run for 10 hours, so this program cannot be completely relied upon to show all memory problems.
Thanks for your help Chris (CPHarris).
I note that there are numerous other threads here that have the Corsair 1600 c9 memory as a common factor!
Nigel
bought same ram and i think mines fixed also the corsair ram is very unstable it seems thanx nige
