Bug in security update? (USN-143-1)

[dylanby]

When I installed Hoary a few months ago, I installed it into a computer
with two hard drives (hda & sda). Initially grub was on hda (hd0)
booting Hoary on sda (hd1). I've since altered the hard disk boot
priority in the BIOS to make sda=hd0 & hda=hd1. I also moved grub to sda
& altered the menu.lst accordingly.

After the recent security update (USN-143-1), grub was changed to look
for boot on (hd1,1) instead of (hd0,1).

Can anyone tell me why this happened?