Are you booting wih grub? I don't know whether grub needs those initrd-... files. And there is the mkinitrd command to make them, if we could figure that out. How nice to be using Linux and have no end to the unanswered technical questions! And I don't know if the insmod command would install the loopback module if support is "disabled" in the kernel configuration.
One simple try would be to do a yum update and get the latest kernel. If you use grub, it just gets added to the list of boot options.
"Never let the task you are trying to accomplish distract you from the study of computers."