Using Ubuntu's USB Startup Disk Creator (USB-creator-gtk), I created a LiveUSB from the Xubuntu 9.10 LiveCD. When booting, it stalls up with the Xubuntu mouse splash screen displayed.
In attempting to troubleshoot, I used Ctrl-Alt-F1 to check out the first virtual terminal. On that screen, I see over and over again the lines:
stdin: I/O error stdin: error 0 /init: line 1: can't open /dev/sr0: No medium found