OK, then it's like some boot option is missing for Arch kernel, e.g. root disk or such has to be passed in a different way. You can edit /boot/grub2/grub.conf directly, too, and correct the boot options. Try to strip down as much as possible, and use a simpler path like /dev/sda1 for root partition instead of UUID. Basically just passing root=xxx should suffice for booting up.