DIMM only works in Bank 2

I am trying to add a 128 mb DIMM to an Intel D815EEA mother bd. The system runs fine with one 128Mb DIMM in bank 2. I have another identical DIMM, when I add it to either bank 1 or bank 0 the system will not boot. I have tried each individual DIMM by itself in bank 2 and everything is fine. Any DIMM installed anywhere but bank 2 and it won’t boot. No video, no beeps, nothing. The trouble code on the LEDs references “Memory auto size, shadow” I have updated the BIOS, with the most up to date version from the Intel site. tried aotu and manual set up. Nothing seems to work… Any suggestions?? What am I missing??