I upgraded my Ubuntu box from 12.10 to 13.10, and amazingly it worked flawlessly, but then I got cocky and upgraded to 14.04 to get on a LTS version.
This of course did not work.
I am dual booting, using the Windows Boot Manager, but when I chose the Ubuntu option, I would get a black screen and a fast blinking cursor. And nothing…
I had to re-do the creating to the boot bits needed for this configuration, which I did by booting to a liveDVD, and doing the following:
dd if=/dev/sdX of=/mnt/ubuntu/System/ubuntu.bin bs=512 count=1
Where sdX is the boot partition, and my Windows partition was mounted at /mnt/ubuntu/System, and I had previously configured (using bcdedit) the Windows Boot Manager to boot from the ubuntu.bin file.