Unity and lots of other things gone

[thinkswithportals]

I think this is the correct place to post this. I powered off my computer last night, (had installed Kingsoft Office, Kontera and Virtualbox, in case you wondered what I most recently did,) and when I powered it back up, the first thing I noticed was that Docky was gone. I checked in the Activities overview Apps menu, (I use Gnome) and sure enough, it wasn't there. I figured It must have somehow accidentally uninstalled, so I looked for the Ubuntu Software Center in the Apps menu to reinstall it-it wasn't there either! Neither was the Terminal, or any of the alternative terminals like UXTerm that come with Ubuntu! I thought it could be a GNOME problem, so I logged out and tried to change my session, but-surprise! Unity wasn't available either! I am kind of panicking as I write, as I have no Idea what could have happened. The only things I downloaded were from reputable sourrces (OMG Ubuntu, virtualbox.org and the Software Center) and Ubuntu never gets viruses anyway. Can anybody help? Should I restore from a backup from a while ago (I sopped doing scheduled backups about two weeks ago) and if so, how?

[dino99]

while booting , hold "shift" key down at the bios end process to get the bootloader menu (grub), and select the second line to boot on "recovery mode"
then select the network line to activate it, and then select "dpkg" to fix (if needed) the system; when done, select "resume" to continue booting as usual.

[thinkswithportals]

Thanks for your help, dino99. Will this work if I have my computer dual-booting Windows and Ubuntu? Also, do I hold Shift at the blueish-purpleish boot screen or the moment the PC boots up?

[thinkswithportals]

UPDATE: Just tried it, got to the GRUB menu, went to the second line, then second line again, did Network, then dpkg, then it told me some graphics drivers would fail and that I could just restart from the boot screen. I did, and the same problem occurred. Did I make a mistake?