A couple of thoughts for you...
If your root folder is located on partition 6 of hdc then root(hd0,x) should be 5. This parameter specifies the number of partitions BEFORE the one you want to use. The kernel line should specify the actual device which would be /dev/hdc6.
Also, what is the content of /boot/grub/device.map? This maps the GRUB hd0/hd1/hd2... etc to physical devices. I *think* it is supposed to follow the boot order of the drives as set in your BIOS.
Below are two example entries for you, whenever you modify the device.map file, re-run: #grub-install /dev/hdc
title Ubuntu, kernel 2.6.17-11-generic
kernel /boot/vmlinuz-2.6.17-11-generic root=/dev/hdc6 ro quiet splash
Hope it helps.