My laptop is a Lenovo ThinkPad Edge 14.
What happened is that I made a stupid decision which delete some important packages and cause cannot access the network and thus I have to reinstall with the CD.
While reinstalling. It prompts that there is a problem with installing one package (sorry I forgot the name) and said I should manually fix it after reinstall.
After reboot, I chose the first one from the boot menu (ubuntu, advance option, memory testing...). I did not need to choose before reinstall, strange..). It always has the message "Error occurred while mounting /boot." "Press S to skip mounting or Press M for manually fix".
Skip it and it can bring me to functional "Desktop" but with strange resolution. The the icon/text is scaled to make it look "wider".
And also it is a bit slow comparing with "before reinstall".
I don't know whether these two problems are caused by "Error occured while mounting /boot." But that's all I notice.