cannot upgrade kernel, not a space problem

[oxy]

Dear all,

since weeks the software updater of my ubu 14.04 (64bit) is falling to
upgrade the kernel. It does not seem to be a space problem:

----------------------- code + output -----------------------
# df -h

/dev/md5                  1.3T  772G  476G  62% /
none                      4.0K     0  4.0K   0% /sys/fs/cgroup
udev                      7.9G  4.0K  7.9G   1% /dev
tmpfs                     1.6G  2.1M  1.6G   1% /run
none                      5.0M     0  5.0M   0% /run/lock
none                      7.9G   13M  7.9G   1% /run/shm
none                      100M   72K  100M   1% /run/user
/dev/md2                   28G   46M   26G   1% /tmp
/dev/md0                  1.8G  381M  1.4G  22% /boot
/dev/md3                   28G  5.9G   21G  23% /var
-----------------------------------------------------------------------

Pls have a look at some error msgs:


----------------------- code + output -----------------------
# sudo apt-get upgrade -f

Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  fglrx
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
2 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n]
Setting up linux-image-3.13.0-48-generic (3.13.0-48.80) ...
Internal Error: Could not find image (/boot/vmlinuz-3.13.0-48-generic)
dpkg: error processing package linux-image-3.13.0-48-generic (--configure):
 subprocess installed post-installation script returned error exit status 2
dpkg: dependency problems prevent configuration of
linux-image-extra-3.13.0-48-generic:
 linux-image-extra-3.13.0-48-generic depends on
linux-image-3.13.0-48-generic; however:
  Package linux-image-3.13.0-48-generic is not configured yet.

dpkg: error processing package linux-image-extra-3.13.0-48-generic
(--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a
followup error from a previous failure.

                                   Errors were encountered while
processing:
 linux-image-3.13.0-48-generic
 linux-image-extra-3.13.0-48-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)
-----------------------------------------------------------------------

 Can anyone tell what is going on here?

Thx in advance!