I, also, can confirm this issue. The ONLY remote MD I have had running AT ALL was on an HP L2105CA / AMD Turion 64 / 1G DDR / 80G SATA HDD / ATI Xpress 200M / Display panel removed, due to backlight failure, uses external 19" flat-panel.
I attempted to leave all but 2Gig swap unpartitioned, to use as diskless MD, and give the unpartitioned disk-space to the Core to use as it pleased. However, I cannot get this or any of two other machines to succeed at even a single PXE boot, so installed Kubuntu / LMCE as per instructions (CD's), and IT WORKED!!! Until 45 minutes after it was running, when it did exactly what you have described here.
I'm primarily troubleshooting the PXE issues at the moment, but I'm glad I'm not the only one with this issue, and hope that you do receive some info as to how to solve it. Please, if you do get it fixed, post it here, as I'll be keeping an eye out. I'll do the same, very definitely.