Even if I choose advanced boot loader options and tell the installer that hdc comes before hda in the boot sequence, it doesn't offer me an option to install the boot sector on /dec/hdc (only /dev/hda). Even though I thought it might end up installing the boot sector on /dev/hdc anyway, it did not, so I ended up with a system that couldn't be booted, and /etc/grub/devices.map had (hd0) for hda and (hd1) for hdc, which is exactly the converse of what I specified in the configuration screen, and grub.conf was full of references to hd1 for partitions that should be in hd0. If I change the boot order, this should be relected in devices.map, grub.conf and also in the options offered for where to install the boot sector.
This works for me here. I go to advanced boot loader options and move hdb up by clicking the up arrow and things change to reflect that.
I must have done something stupid such as selecting the disk but not moving it up. It does work, indeed.