I was upgrading my ubuntu 13.10 to 14.04 and was having this exact Ubuntu 14.04 doesn' t boot after upgrade from 12.04 installed inside Windows 8.1 problem.
I have been able to start my system but I want clarify that should I change all the occurrences of 'ro quite splash' to 'rw quite splash' in grub.cfg? There are two places that 'ro quite splash' occurs in grub.cfg file. I am very new with ubuntu. Please help.