Doesn't like the physical layout of the memory as installed. The rules
are:

* Memory must be installed in DIMM pairs.
* The capacity of DIMMs within a pair must be the same.
* Install DIMMs with the greatest capacity in the lowest t
numbers.
* Install DIMMs the following slot order: 0a/b, 1a/b, 2a/b, 3a/b, and
so on.

Refer to this page:
http://docs.hp.com/en/A5191-96022/ch01s03.html