It loks as if the new advanced format drives may have something to do with it. reading furthe in the wikipedia link I posted, I found this...
For disks that present a sector size other than 512-bytes, there are limitations as well. A sector size of 4,096 results in an eight-fold increase in the size of a partition that can be defined using MBR, up to 16 TiB−4,096 bytes.[citation needed] Versions of Windows more recent than Windows XP support the larger sector sizes as well as Mac OS X, and the Linux kernel has supported larger sector sizes since 2.6.31[17] or 2.6.32,[18] but issues with boot loaders, partitioning tools and computer BIOS implementations present certain limitations.[19]