[ubuntu] Ubuntu Freezing and grup corrupting

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http://ubuntuforums.org – Hi, I installed ubuntu 12.04 along with Windows 8 as dual boot system on Sony Vaio F11 laptop. When I run Flash video (youtube, espn3) ubuntu seems freezing the whole system..I happened to do cold reboot few times which allows me to get back to ubutu...Then later I was reading about Magic Recovery Key ( Alt+PrntScreen+R+E+I+S+U+B) and tried when it frozen again.. This time it restarted but shows up message as "Operating SYstem Not Found"... Later I was able to restore grub using Live CD + Boot Recovery tool..here is the dump http://paste.ubuntu.com/1188086/... I just wa (Hardware)