There should be options to allow CD/DVD boot with file deafult.xbe
Make sure in X3 Config Live -> Customize X3 Bios -> Disabled CDrom Boot = Disabled.
And in X3 Config Live -> Other Startup Tweaks -> DVD Boot XBE Name = default.xbe
If this is set, then try a different type/brand of CD/DVD. If it is a CD-R, try a CD-RW or DVD-R or check what is compatible with your drive.
If you want to go straight to a dashboard and run a game from the dashboard you can do that as well...
X3 Config Live -> Customize X3 Bios -> Autostart X3 Config Live = Disabled.
To get back into X3CL, hold the white button during boot up.