How do I make a bootable USB stick from an ISO image? I'm running Kubuntu 12.04

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http://askubuntu.com – Why won't kb3 (in Kubuntu 12.04) recognize a USB drive and allow me to burn an ISO image to it? kb3 is the default iso burning application and it gets generally good reviews. But it pops up a dialog telling me that I don't have an optical drive and it refuses to allow me to select the USB drive. What am I overlooking? The computer is a ThinkPad X220 tablet without an optical drive. What's another recommended way to burn an ISO to a USB drive in Kubuntu? The ISO is for a firmware update utility. (My question is not about how to install Ubuntu.) (HowTos)