v7.2.0 won't boot from my USB stick

I put v7.2.0 on a DVD and booted from it. I used the flash-knoppix option from the GUI to put it on my 16 GB Patriot stick. I've tried booting from it on several machines, but none will boot from it. Some just hang and others ignore the drive and boot windows even though I put the USB stick at the top of the boot order. I made a similar USB stick with v7.0.5? on it, it boots fine. I poked around the internet for ideas. I found a suggestion to use install-mbr on the USB stick. Unfortunately, when I do apt-get install mbr, I get a not found message even though my sources.list points to wheezy and when I looked there, mbr was listed. I know computers, but I'm not yet well versed in Linux or Knoppix. Can you help me?