I know there are several threads on this topic out there. But I still cannot find the solution. I'm trying to fix grub from livecd but it doesn't recognize /dev/sda at all. Is there a way to mount sda so that I can reinstall/repair grub?

Have you the correct drivers loaded? I am a believer in a usb drive as an essential piece of equipment. I have an ide/sata one and can shove any disk in for test/repair purposes. Useful, as it's the only ide reader I have now.

can you access the smart info of that drive?

There was no way I could check SMART data on that drive, nor access its info. The chances were: hardware issue (the drive has only a few months old), or the system (software) was corrupted in some way. There was nothing I could do to repair grub (not that I knew ;-/ ) given that it was inaccesible. To avoid any data loss, I disconnected the disk where personal data is allocated (sdc), just in case, and then, used this cables with the failing disk, in order to make sure everything was working fine. Turned on the pc and for my surprise it recognized sda, eventhough the grub was corrupted. (At this point, I was pretty sure It was a cable or motherboard issue, slots perhaps?). Don't remember why is it that I couldn't repair it from live session (the grub), and I'm not an advanced linux user either, so I installed a distro in a free partition I had available, so that during the process of installation it would set up grub as well. It worked. Perhaps, not the quickest, nor the smartest, but worked. Lastly, I wanted sdc (personal files) working too, so I put cables back to its respective drives, and both worked properly till now!!!
Crazy, isn't it?

Now that I am back again, with everything working out of the box, I checked drive's status within "disk utility" (gnome). Disk has no errors.