Comment 2 for bug 1191316

Thank you for taking the time to report this bug and helping to make Ubuntu better. To make certain that this is a bug I would like to to check a couple of things. In a terminal enter "df -h" and paste the output here. Sometimes /boot is a separate partition that can run out space if there are many old kernels installed and that could cause this error.

If there is no space left on /boot you have to remove some old kernels to make space. I will also mark this bug as a duplicate of #798414 which deals with this error.

You can manually remove old kernels by following these instructions:
https://bugs.launchpad.net/ubuntu/+source/initramfs-tools/+bug/798414/comments/10