[xubuntu] Boot repair says drive is mounted

I don't know what caused this issue. I downloaded some seemingly benign updates to a Xubuntu instance I run in VirtualBox, and now it won't boot:



So I downloaded the boot recovery ISO and attached it to the machine, it seems to run fine, but then I get this message:



This makes no sense to me, since when I check in GParted, it's not mounted:



In case it's helpful, here's the Drive-repair information dump: http://paste.ubuntu.com/14487560/
Any help would be very, very much appreciated.