I'm using Ubuntu 13.10 and I've been using for a while now as ran it from a daily build about a month ago. It's fully updated with updates, upgrades an dist-upgrades and it was working up until very recently. Not sure exactly when I last issued a Ctrl+Alt+T as I quite often just leave it running however it will have been certainly in the last week. Basically when I hit that key combo I do not get a terminal. I know that each of the keys function as I can Atl+Tab through open applications and I can Ctrl+C to copy and past Ctrl+V to paste and I've typed plenty here that has a "T" in it. I have checked Keyboard Layout in Settings and the correct combo is assigned to the terminal. You'll have to take my word for that as I'm not allowed to post my screenshot!!!!!