[other] Unable to boot

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http://ubuntuforums.org – Hi, I have a dual boot computer (Ubuntu 11.10 or 11.04 / Win7). Everything was working fine until yesterday when it froze while I was under Win7, after that I can't boot the computer anymore and it keeps restarting. The restart occurs right before the when the grub should start (I can't see the grub at all). I've tried to boot from Ubuntu live CD, but that doesn't also work. I got this alert from 9.04, when I tried to choose "try ubuntu without installing it" from the menu. Code: Boot loader /casper/vmlinz This one from 10.4 Code: boot loader live: file not found And 11 (Hardware)