I power off my laptop with Ubuntu 11.10 during apt-get upgrade, then I power on and choose Ubuntu in grub, but after the Ubuntu logo, a blurred screen comes.

Then I choose recovery mode in grub, and then I can type commands as root,

I tried apt-get upgrade and it tells something wrong with /var/lib/dpkg/lock, and suggest dpkg --configure -a, then I tried dpkg --configure -a but comes something wrong because read-only file system, then I have no idea..

Any suggest will be helpful.