So I have been using linux mint for a while now. A few months ago my Gnome shell crashed and I was unable to use the full 3d features and loaded into fallback mode only. From that day (around 2 months ago) I still have only fallback mode (both Gnome and cinnamon). I installed Linux mint maya, and Ubuntu 12.04 both as windows file and complete installation in an external hard drive. and for many times I sitll cannot fix this problem. ps I made sure to download all the drivers for my graphics card. what could the problem be?