I have been having this strange problem for a month or so. I have installed Ubuntu 14.04 alongside Win8.1 on my Lenovo z510. It worked fine for about 5 months, but almost a month ago, I started getting error at the grub menu in grub
grub rescue>filesystem is unknown. Sometimes I also used to get a
error:trying to read/write outside hd0 or similar.
A workaround was a few restarts, or a manual set of
from the rescue prompt was to be done.
I got fed-up with this and overwrote grub with the windows bootloader. This time, it worked(although it boots directly into Windows). I never got any error while booting. Yesterday I reinstalled ubuntu hoping it will work again but it is just like before. Anyone has any ideas/solutions on how to get ubuntu working?