Answer by Marc for Problem With Unetbootin (Or, Perhaps, Me)

I've given up on unetbootin. I download the .iso to my home directory and use dd.

In a terminal window, you'd type sudo dd if=inputfile.iso of=/dev/sd* bs=1M where inputfile.iso is your lubuntu iso, /dev/sdc is the usb thumb drive and /dev/sdc is the device your usb thumb drive is. Get the if and of right, because dd will overwrite stuff in a flash.