Join the club of unsupported customers.
I have a Linkstation Quad and have the same problem.
Buffalo only supports 3TB drives if you buy one of their new products.
They have NO intention of supporting 3TB drives on any of the OLD products, including the ones that are in the stores and being sold within the last few months. Buffalo will also NOT release the firmware code in order for us to do the very minimal recompile in order for the units to support 3TB drives. All of this is because it would cut into their profit margin to have perfectly good hardware support current backup devices such as the WD 3TB USB drives. So, I am sorry to say, but you are stuck like MANY MANY more of us are, with unsupported hardware, still within the warranty period, but without the functionality they promised on their website and at the store, like "Plug your USB drive int o the USB port...", only they forgot to tell you that it had to be an OLD or SMALL harddrive...
Enough ranting, but the answer is an I quote their customer service "Buffalo has no intentions or plans on supporting drives over 2TB on any of the OLD hardware"