A couple of comments on the link that Dugan provides.
1. Linking to /dev/dvd in my case didn't work as the link got removed on reboot (udev?) Do:
to see what the raw device is acutally linked to. Give that info to gxine or xine.
2. If the method of enabling DMA given doesn't work. Try adding:
to lilo.conf. Using Boot Manager ("Start button" / Settings / System Administration / Boot Manager (LILO) makes it easy.