I was trying to create a LiveUSB with my SanDisk Cruzer on Ubuntu with the Startup Disk Creator program, then because of some reason it could not boot. I guess it was because I checked the Format USB option when I created the disk. After some time I wanted to install Ubuntu 11.04 through the USB, so I formatted the USB and used Pendrivelinux to create the LiveUSB (I was on Windows at that time). But the problem is that now my USB won't boot.
Theres a good chance pendrive did not load an instance of grub on the USB Key that your bios could utilize/find. I know when i use DD to create my usb images, it depends on the format of the iso. Occasionally i have to specify the device node itself, or speicfy the first partition on that device.
dd if=awesomeness.iso of=/dev/sdc OR dd if=awesomeness.iso of=/dev/sdc1
so verify that you're writing the image properly to the usb key if your BIOS boot order has been changed. If pendrivelinux continues to fail to boot, you can always give the official LIVE CD a go and verify its not due to a poor image.
Try using unetbootin
There are versions for Linux and windows, on ubuntu you can install it with
sudo apt-get install unetbootin mtools
mtools is required for unetbootin, on some distros is installed by default, on ubuntu you need to install it.
just run that program, chose Iso File option and select your iso..