Ubuntu Server 13.04.3 doesn't boot with EFI

Knowing more about your setup may be helpful. In particular, you mention using OS X to prepare your boot medium, but you also don't mention any OS X partitions, so it's not clear if the computer is a Mac or some other type of computer. If it's a Mac, I recommend you post back with clarifications, including whether you've actually got an OS X installation on this system. If it's a UEFI-based PC, one of the following will probably get things up and running:

• If Secure Boot is enabled on your computer, disable it. Then download and prepare a USB flash drive or CD-R with my rEFInd boot manager. (Note that there are download links for images of both type.) Boot with it. This should get Linux booting. You can then install the Debian-package version of rEFInd, which should take over the boot manager duties on your computer.
• Run the Boot Repair utility from an emergency disc booted in EFI mode. In many cases, this will get GRUB working again. In case it doesn't, be sure to record the URL that the program presents. You can then post it here, since it will hold additional details that may be of use in diagnosing your problem.

If you've got a Mac, rEFInd is likely to be the more useful tool, but you should install it from OS X, not from Linux. (That is, don't use the Debian package; use the .zip file from OS X.)