exclamation point appear in gparted after creating startup disk

[G.]

I was attempting to install chrome os to a usb following instructions
on   http://chromeos.hexxeh.net/.

I entered sudo dd
if=ChromeOS-Vanilla-2284.0.2012_05_15_1652-r6b1abb2a.img of=/dev/sda
bs=4M

The installation on the usb failed, I received no error messages, but
when I loaded gparted there were new listings (I tried to attach a
screen shot but the list kicked it back).

I also see c-state and c-root entries in Nautilus.

I received the following when I tried to list the partitions in terminal:


WARNING: GPT (GUID Partition Table) detected on '/dev/sda'


I would appreciate any assistance you can give.

I am using Ubuntu 12.04 and everything appears normal at this time otherwise.

Thanks

garyk