OK, started looking at the drives in the RAID and realized something interesting... The 1.74 firmware is dropping the uImage files into the first partition as "uImage-88f5182.buffalo" and "uImage-lsp.5.x.buffalo". When I am re-building the drives from scratch, I set up drive 1 with these files, but had to rename the "uImage-lsp.5.x.buffalo" to "uImage.buffalo" for it to work. After the latest firmware load and E06 errors, I pulled the first two drives and checked the first partition. The uImage-lsp filename is not updated, as well as the RAID was still showing four drives instead of two. I renamed the file on both drives and put them back into the NAS. Booted it up, the drives resynced and I started getting an E16 instead. Added the two other drives, rebooted, they all synced , and now the NAS is back up and operational. That seems like a very wonky thing for the firmware names to cause that issue, especially given that it is the firmware from Buffalo that is causing it.
Thanks for all of your help and hopefully this helps someone else!
B