I have gone back through MaG's w/t and am pretty certain that I have done everything correctly, I know it is the correct datapad because it came from the corpse, and it did work at first, but I could see that it was going to take a while to solve so I saved and went back to it which was when it appeared corrupted. I did have trouble downloading the game because Norton took exception to it, so I will go back and turn Norton off and re download the patch, also I intend to delete the last few saved games and replay them according to the w/t. Will let you know how I get on

Thank you for your comments.