I am facing an issue when I did following. Initially my pc had Windows 7 ultimate x64 installed. Then I made it dual boot with Ubuntu 12.04 x64. Everything used to work fine then.
Problem started when I upgraded Windows 7 to Windows 8 pro. After my upgrade I list grub loader. I was not getting any option to select OS. Then I googled the issue and somehow I do not remember exactly how, I fixed that issue. I am now getting OS option at boot time.
However sometimes usually after installing any updates in Ubuntu I do not see grub loader at boot. Sometimes it appears sometime is does not. I have figured out that this usually happens after Ubuntu update. To fix that issue I run boot-repair and repair system with recommended button. This solves the issue temporarily until Ubuntu update.
By ubuntu update I do not mean Ubuntu version upgrade, update means the security fixes and kind of stuff.
My recent boot repair log can be found at: http://paste.ubuntu.com/5666240/
I am not that much technically familiar with linux machines so any advice will be appreciated.