I wont be suprised if its the ati x200 chipset thats screwing things up...
See my comments in this post:
http://osx.kbot.de/comments.php?DiscussionID=181&page=1
I installed tiger through vmware and than installed the ata driver so tiger works reasonably well now.
I'm still trying to get leopard so have not tested it native nor through vmware..

uphuck also has a nice comment about it on their site:
http://www.uphuck.com/Uphuck%20OSX86%20Development/dvdsupport.html
once again I did get it to work though using the different ata driver but if its compatible with leopard I do not know..