Running a straight "apt-get update" and "sudo apt-get update" had no effect on the error, so I went into the MD's sources.list and made the following changes:
FROM
deb
http://archive.ubuntu.com/ubuntu/ gutsy main restricted multiverse universe
deb
http://archive.ubuntu.com/ubuntu/ gutsy-security main restricted multiverse universe
deb
http://archive.ubuntu.com/ubuntu/ gutsy-updates main restricted multiverse universe
TO
deb
http://old-releases.ubuntu.com/ubuntu/ gutsy main restricted multiverse universe
deb
http://old-releases.ubuntu.com/ubuntu/ gutsy-security main restricted multiverse universe
deb
http://old-releases.ubuntu.com/ubuntu/ gutsy-updates main restricted multiverse universe
I reran apt-get update on the MD and saw a bunch of updates load.
However, upon running "sudo apt-get install xfsprogs" I was greeted with a boatload (pages, literally) of unmet dependencies and offered the option of running "apt-get -f install" to correct. I then ran "sudo apt-get -f install xfsprogs" just to see what would happen and I again was presented with pages of packages that were going to be updated upon pressing Enter.
I didn't. I know it's "just" a diskless MD, but the wholesale upgrade of just about every package on the MD to install a package that loaded without incident on the core seems suspicious.
However, now that I think of it, there *is* a difference between the LMCE systems on the core and the MD. While I don't know much about this stuff, the core is a P4 running a standard 386 package set and the MD is an Intel Dual Core which I believe is running an AMD (kernel?) which came up as part of the MD's diskless autoconfiguration. Perhaps this explains the different behavior vis-a-vis the xfsprogs package on the core and the MD?
Mark