Teste isso:
Abra um terminal
Pressione Ctrl + Alt + T
Execute:
sudo -i
apt-get update
apt-get autoremove
apt-get clean
UNUSCONF=$(dpkg -l|grep "^rc"|awk '{print }')
apt-get remove --purge $UNUSCONF
NEWKERNEL=$(uname -r|sed 's/-*[a-z]//g'|sed 's/-386//g')
ADDKERNEL="linux-(image|headers|ubuntu-modules|restricted-modules)"
METAKERNEL="linux-(image|headers|restricted-modules)-(generic|i386|server|common|rt|xen)"
UNUSKERNELS=$(dpkg -l|awk '{print }'|grep -E $ADDKERNEL |grep -vE $METAKERNEL|grep -v $NEWKERNEL)
apt-get remove --purge $UNUSKERNELS
update-grub