I have the same problem with X11. During installation customization, I checked X11 option, and the installation went smoothly and the system ran right after reboot. But when I tried X11, looks like nothing happened, although when I open the Console to see the log, it does go thought some procedures about X11. I don't have any error message though.

I will try to reinstall X11. One question: what should I do to reinstall X11? Should I run the installation dvd in Leopard? or should I boot using dvd and reinstall the whole system?

Thanks for any help.