Having the same problem as this thread that was closed before the issue was ever solved for some reason, blocking upgrade to saucy.
The problem is definitely GRUB. The drive is correctly formatted; I do have a UEFI system; I have installed grub to this drive before. GRUB is probably looking for something it shouldn't be, like an arbitrary file on the drive or a particular partition table format that isn't valid across different kinds of systems.
Unfortunately I have to say there's never been anything easy or straightforward about installing GRUB with EFI. Nearly every attempt has resulted in an unbootable system because of errors in how GRUB installs itself, misreads partition tables, etc. So, knowing that the problem is once again in GRUB, how can I convince GRUB that in fact my EFI partition is an EFI partition?
Alternatively, can I convince GRUB not to check if an EFI partition "looks" like whatever it believes an EFI partition should look like?
The problem is definetly grub, unless the problem is a bug in all (ubuntu) linux kernels after 3.5.0 which is causing efibootmgr to crash and occasionally lock up the computer.