Red Hat by default disables DMA on cdrom/dvd drivers. They do this to avoid problems with flakey hardware.
Enabling DMA has changed on 8.0 over previous releases. Add this to your /etc/modules.conf
options ide-cd dma=1
This setting will not take effect until you unload/reload the ide-cd module. Or reboot.
You can unload a module with:
Note if the module is being used by something else you have to remove that module(s) first.
load a module
Note: insmod and modprobe behave differently. Check out the manpages on them for more details.
You can view what modules are loaded with: