Booting Problem

[sam]

Hello, 
I will appreciate it if someone can help me with this issue
1-      I upgraded my system from Ubuntu 10.04 to Ubuntu  11.10. but unfortunately, I faced a problem. The system will not boot and hang.
2-      I tried to Install Boot-Repair via live USB (since I can't access the operating system without booting)
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install boot-repair
 
3-      Unfortunately, I faced another problem. I got this error:
            sudo: can't stat /etc/sudoers: Input/output error
            sudo: no valid sudoers sources found, quitting 
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