I don't think theres anything you've failed to do. As far as I know you plug it in and it works you shouldn't have to alter anything. I would try running memtest and see if it finds anything, its on the latest DVD on the mag I think or you can download it.
I suspect either the new memory has a fault or its not exactly compatible with the board, it has a slight difference and that is stopping it working properly.
Can I ask where you bought the memory and how you decided it was the right stuff as some boards are very touchy about what you can use?