I encountered this problem while ...
I encountered this problem while I was doing the upgrade for the guest additions of VirtualBox.
Guest OS: Ubuntu 14.04
Remove the following symlinks before you install the new version of the Guest addtions
# rm /usr/lib/x86_64-linux-gnu/VBoxGuestAdditions
# rm /usr/lib/VBoxGuestAdditions
# rm /usr/share/VBoxGuestAdditions
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