Keyboard layout change in Ubuntu

I've had this problem a couple of times in my Ubuntu machine. I installed it with US keyboard layout, and then changed it to UK later (for my user). Even when I select the correct keyboard model (Generic 105-key (Intl) PC), and layout (United Kingdom International) some keys still act weirdly (e.g. pressing " does nothing, and if I press it twice I get a strange "-like symbol). I fixed it by running:

sudo xmodmap /usr/share/xmodmap/xmodmap.uk