You are very welcome,
If you look closely at the System Board diagram on Page 90 and the description of the connections below it, you will see that #10 (white slot) and #11 (black slot) make up Channel A. This means that you would populate them together. While #12 (white slot) and #13 (black slot) make up Channel B. As I read it, this means that you would populate these slots together. Also, it is always best to use the same speed memory modules together. Using different speeds can cause conflicts.
It appears that you have populated the Channels A & B this way, but with memory modules of different speeds. Try the same speed modules in A to see what happens.
