I have used UNetbootin to make a 4GB USB stick into a bootable media but keep running up against the same problem.
I removed the partitions and formatted the USB drive as MBR and added a single FAT32 partition. Then I cleared the /tmp/ directory and had UNetbootin make an Ubuntu (AMD64) bootable disk on the USB device. The bootable flag is set, the files etc look correct but on more than one device I get the error message that this is not a bootable device.
What has gone wrong and how do I fix it?