Same issue here with a LS420D0402. Both drives shot, second time this has occurred to me with this unit, both times using RAID (mirrored drives), both times BOTH drives failed simultaneously. I'm about ready to give up on Buffalo and use a different brand going forward.
Why the heck are they booting from, and ALL firmware stored on, the DISKS?
So if the HD fails, these units is GARBAGE??? What the heck were they thinking? This seems absolutely RIDICULOUS.
So there is no way of booting from a USB stick or something, and reloading the firmware onto new disks?