Hi,

I am also meeting with this issue, in Xubuntu Trusty latest version : 14.04.3. I can fix it by forcing the install of the missing depends which in return replace all the lts* packages for their non lts equivalent.

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$ sudo apt-get install virtualbox-guest-x11 virtualbox-guest-utils
Reading package lists...
Building dependency tree...
Reading state information...
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 virtualbox-guest-x11 : Depends: xorg-video-abi-15
                        Depends: xserver-xorg-core (>= 2:1.14.99.902)
E: Unable to correct problems, you have held broken packages.
# apt-get install virtualbox-guest-x11 virtualbox-guest-utils xorg-video-abi-15 xserver-xorg-core
Reading package lists...
Building dependency tree...
Reading state information...
The following extra packages will be installed:
  dkms fakeroot libfakeroot libgl1-mesa-dri libgl1-mesa-glx libglapi-mesa
  libllvm3.4 virtualbox-guest-dkms xserver-xorg xserver-xorg-input-all
  xserver-xorg-input-evdev xserver-xorg-input-mouse
  xserver-xorg-input-synaptics xserver-xorg-input-vmmouse
  xserver-xorg-input-wacom
Suggested packages:
  dpkg-dev debhelper libglide3 xfonts-100dpi xfonts-75dpi touchfreeze
The following packages will be REMOVED:
  libegl1-mesa-lts-vivid libgbm1-lts-vivid libgl1-mesa-dri-lts-vivid
  libgl1-mesa-glx-lts-vivid libglapi-mesa-lts-vivid libgles1-mesa-lts-vivid
  libgles2-mesa-lts-vivid libwayland-egl1-mesa-lts-vivid
  libxatracker2-lts-vivid xserver-xorg-core-lts-vivid
  xserver-xorg-input-all-lts-vivid xserver-xorg-input-evdev-lts-vivid
  xserver-xorg-input-mouse-lts-vivid xserver-xorg-input-mtrack-lts-vivid
  xserver-xorg-input-synaptics-lts-vivid xserver-xorg-input-vmmouse-lts-vivid
  xserver-xorg-input-wacom-lts-vivid xserver-xorg-lts-vivid
  xserver-xorg-video-all-lts-vivid xserver-xorg-video-ati-lts-vivid
  xserver-xorg-video-cirrus-lts-vivid xserver-xorg-video-fbdev-lts-vivid
  xserver-xorg-video-intel-lts-vivid xserver-xorg-video-mach64-lts-vivid
  xserver-xorg-video-mga-lts-vivid xserver-xorg-video-neomagic-lts-vivid
  xserver-xorg-video-nouveau-lts-vivid xserver-xorg-video-openchrome-lts-vivid
  xserver-xorg-video-r128-lts-vivid xserver-xorg-video-radeon-lts-vivid
  xserver-xorg-video-savage-lts-vivid
  xserver-xorg-video-siliconmotion-lts-vivid
  xserver-xorg-video-sisusb-lts-vivid xserver-xorg-video-tdfx-lts-vivid
  xserver-xorg-video-trident-lts-vivid xserver-xorg-video-vesa-lts-vivid
  xserver-xorg-video-vmware-lts-vivid
The following NEW packages will be installed:
  dkms fakeroot libfakeroot libgl1-mesa-dri libgl1-mesa-glx libglapi-mesa
  libllvm3.4 virtualbox-guest-dkms virtualbox-guest-utils virtualbox-guest-x11
  xserver-xorg xserver-xorg-core xserver-xorg-input-all
  xserver-xorg-input-evdev xserver-xorg-input-mouse
  xserver-xorg-input-synaptics xserver-xorg-input-vmmouse
  xserver-xorg-input-wacom
0 upgraded, 18 newly installed, 37 to remove and 0 not upgraded.
Need to get 15.1 MB of archives.
After this operation, 47.7 MB of additional disk space will be used.
Do you want to continue? [Y/n]

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