During the course of my investigation as to the strange happenings with H/W Accelaration, one of the steps I took was to restore my BIOS to the "default" settings. As I run a RAID mirror system, this in hindsight was a particularly stupid thing to do - as my System switched out of RAID Mode and back into "standard" IDE Mode. When one attempts to restart again it won't boot up and you get warnings from Windows that the MBR is missing and requesting you to carry out a Windows repair by putting the original installation CD in the reader. Windows does recover BUT lots of files go missing and ones Raid drives are no more!
A point worthy of mention was that before my screw up I could not get ATI CCC (V11.2) to unlock the performance mode/hardware acceleration window. I tried reinstalling 10.12 and this seemed oK. When I contacted ATI support - they were incredibly vague and said that they had had instances of 11.2 failing this way and said I should stick with my 10.12(??)
Any way to cut a long (and very painful) story I ended up doing a complete rebuild of the system from the bottom up. Having rebuilt the system I then installed all the latest drivers again (including 11.2 - which now worked!). I then installed PD9 the 2504 patch and the contents patch, this was fine until I tried to enter my software key which it would not accept.
I then removed PD9 et al and did the usual cleanup. This time installed the original PD9 and contents pack. I then entered the product key (which was accepted) and then installed 2504 patch.
All now seems well with the ATI monitor showing lots of GPU activity, doing "silly" things with M2ts clips, splitting them, adding transitions, effects, enhancements etc. don't now seem to trouble PD9 at all. So 2504 is good when installed on a clean base system - ie you don't nee to bother with interim patches.
I am sorry if this rambles on a bit but 1. If it saves someone from the "features" of Intel's Mass Storage Raid system, which it appears erases the metadata from Raid discs and says the data is lost (wrongly - it is not) 2. Highlights the fragility of the software/hardware interactions involved in Video editing. then it may be worthwhile. PD9 is not terribly "fault tolerant" and does need everything just so - but we all know this so its nothing new. The final message/lesson for me from this is that if the system/PD9 starts malfunctioning. Stop and do a complete system rebuild - its painful but it may well be quicker and less stressful than trying a truly analytical appproach.
"Luddite Don"
So make sure you keep your systems properly backed up!
Gigabyte I7/4940 O/C 4.3, Noctua Cooler 10GB DDR3, 4 x 1TB, 1TB SSD, Geoforce GTX660 TI 8500W PSU, Windows 10 Pro 64bit.