ubuntu桌面版修改屏幕刷新率之后无法进入桌面（一直卡在输入密码的界面）的解决办法

deb https://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiversedeb-src https://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiversedeb https://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiversedeb-src https://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiversedeb-src https://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiversedeb-src https://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
## Not recommended# deb https://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse# deb-src https://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse