Problems installing new RAM in Mac Pro - HELP

I just received 4 (2x2 gig) gigs of new OWC 667mhz RAM and almost immediately ran into problems after installation. My goal was to use the 4 gigs of new RAM with the existing 1 gig that came with the machine (2x512 meg). I tried to follow the below diagram as closely as possible, more specifically, Figure 5C for 5 gigs.

I swapped the two 512 sticks to the second empty riser since the diagram shows that the stock 1 gig configuration from apple has the two sticks on the first riser. Then I installed the 4 new gigs in the positions where the original RAM was.

I *thought* everything was fine when I installed the new RAM. The computer booted up and my "about this mac" screen showed 5 gigs. I walked away from the computer for about 2 minutes and in the other room I heard something that sounded like a plane taking off (figuratively of course). I came back to find that the intake fan on the MP was going full tilt! I've NEVER heard that happen before. My screen also had a semi-transparent black bar across the top 1/3 of the screen. I immediately shut down the computer via holding the power button down since the computer was frozen.

I gave turned on the computer and tried again. Again a couple minutes later my screen went dark as if the computer had gone to sleep, but it had only been a couple minutes.

I just pulled out the memory and put everything back to normal and now the computer seems to be working properly again. Is it possible that I installed the RAM in the incorrect slots? Is the computer unstable when running a strange amount of RAM like 5 gigs? I know the RAM was seated completely and so were the risers.

Sorry for such a long post, but I'm hoping it's not bad RAM and just a case of "operator error"

RAM Configuration Diagram
http://att.macrumors.com/attachment.php?attachmentid=82929&d=1187657852

 

I may have answered my own question. Go figure. I found an installation video on the OWC website and it says to install new memory next into riser B directly, which is completely NOT what I did. I'm hoping following the instructions *who'da thunk it* would be a smart thing to do. Hopefully this works.