EndEntire error: premature end of file and
EndEntire error: cannot load image messages might indicate a problem that needs to be fixed from the Windows side -- namely, damage to the Windows boot loader. (OTOH, if you have a backup of your EFI System Partition, or ESP, from before the error occurred, you may be able to recover by restoring that backup. IMHO, such a backup should be made as a matter of course both before and after installing Ubuntu -- but that's another matter.) If I'm right about this, you'll need to get your hands on a Windows recovery disk, use it to fix the Windows boot loader, and then re-install a Linux boot loader or change the boot order so that what you've got now boots first.
I also recommend you re-read my second response to your answer to your earlier question. In particular, prepare a rEFInd USB flash drive or CD-R and try booting with it. This tool (which I maintain) can boot Ubuntu without GRUB, and can chainload to the Windows boot loader, so if GRUB is acting up, rEFInd can provide a workaround -- either temporary or permanent.
Disclaimer: I'm not a fan of GRUB 2. It's a bloated pig of a program with a finicky configuration file that's so difficult to maintain that GRUB provides a series of scripts to perform that task. The result is like a house of cards -- it holds together OK under optimal conditions, but if anything about your configuration is sub-optimal, the whole thing will come tumbling down and be difficult to put back together again. FWIW, my disaffection with GRUB 2 is what motivated me to fork the earlier rEFIt into rEFInd. GRUB 2 has improved since that time, but the fact that I took on maintenance of an open source boot manager rather than deal with GRUB 2 should say something about GRUB 2's problems, at least in my eyes.