When you select (with the arrow keys) the "localboot" option that works for you in UBCD, and before you press "ENTER", please press "TAB". That action should show the Syslinux command line that would be used by that menu entry. Could you please post the exact command?
Additionally, how are you booting UBCD? Optical media? USB drive? Other?
Additionally, how are you booting UBCD? Optical media? USB drive? Other?