Been a while since I'd worked on this, but I decided to rebuild the original server that was brought back from the data center (the one reporting the 256megs) and figured out what was causing it. Someone flipped the "OS Install Mode" to "ON" in the BIOS. This limited the memory to 256megs. What a PITA!
Anyway, toggling that off and rebooting caused the OS to see all the memory.
Hope this helps someone else.