Ubuntu :: Natty Hangs On Boot

When I boot Ubuntu 11.04 it goes as far as showing me the OS options (I dual-boot with Windows7) and then what should be the login window. However - here it displays the mouse and nothing else. It just hangs. I can hit ALT-F1 and get a shell. I login and everything works as expected except X isn't running.

BACKGROUND: I tried to upgrade from 10.10 when (mid-upgrade) my computer turned itself off (suspect housemate unpluged it by mistake and then it ran out of battery). When I turned it on again, it refused to boot, complaining that the / drive was not there. After a bit of digging around I found that it was actually mounting / with read-only permissions. After remounting it with read/write permission I was able to continue with the upgrade. HOWEVER, I never managed to connect to the wireless from the command line (I tried all sorts, sudo iwconfig wlan0 essid "eduroam", sudo dhclient wlan0). Since it hadn't finished to download the new packages, I don't know what it did (presumably installed the ones it did have). Anyway, after doing this I rebooted and everything seemed to work - I logged in and (using update-manager) did a partial upgrade which seemed to work. The only problem was that it was now complaining that nautilus was not configured and for this reason it could not update a package called libglib2.0 or something like that. I tried to repair broken packages/reinstall nautilus etc nothing worked. I then rebooted (I don't remember why I thought that would be a good idea). Since it hasn't given me a GUI login window again. It just hangs, like I said.