Gnome 3 (running on Ubuntu, with the latest nvidia drivers from nvidia’s ppa) shell kept crashing on me when I was typing in the Activities “Search Box”, after some digging, the problem seems to be the recently-used list. If there is anything in it, it crashes things apparently. This seems to work:

echo "" > ~/.local/share/recently-used.xbel

then, to stop it from ever writing to that file ever again:

sudo chattr +i ~/.local/share/recently-used.xbel

Problem solved