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

Why are you trying to "burn" an image to a USB stick? "burning" refers to a laser printing a pattern of holes into the surface of an optical medium, which obviously does not apply to your USB stick.

Give Unetbootin a try, it may actually work (it works for Windows 7 as well).

Alternatively, you could just copy the contents of the image 1:1 to your stick. First, identify your stick with its device name. You can find this information using "Disk Utility" (or search for "palimpsest" in your Dash). It will look like /dev/sdb.

Next, open a terminal and run:

sudo dd if=myiso.iso of=/dev/sdx

Where myiso.iso should be replaced with the path to your image, and x with the correct device letter of your USB stick. NOTE: accidentally entering a wrong device name can result in data loss on other storage media attached, so beware!

Now, your USB drive should contain a 1:1 copy of the image. Try booting it.

Regarding upgrading firmware using linux:

You can refer to this page from lenovo forum. It worked for my x220. http://forums.lenovo.com/t5/Linux-Discussion-Knowledge-Base/Updating-the-BIOS-via-USB-X220-s-running-Linux/ta-p/674677

Here I paste the steps over, but credit goes to writer of geteltorito.pl

1.Get the bios update iso (8duj10uc.iso or later) from the lenovo support site.

2.Get 'geteltorito' and extract the boot image from the iso (isobar.c probably works too)

$wget 'http://www.uni-koblenz.de/~krienke/ftp/noarch/geteltorito/geteltorito.pl'

$perl geteltorito.pl 8duj10uc.iso > biosupdate.img

3.Copy the image to the usb thumdrive

$ sudo dd if=biosupdate.img of=/dev/usbthumdrive bs=512K

Reboot, Press F12 and boot from thumb drive.

From within the software center, or on their page, you can download a very nice program called Unetbootin, which should do what you're looking for!

When you download ubuntu there are some instructions. http://www.ubuntu.com/download/help/create-a-usb-stick-on-ubuntu.
They basically just tell you to run startup disk creator