I'm using Ubuntu 12.04 LTS but now I can't use shortcuts like Right-Left. up-down are working. I installed dconfig-tools and in the path org/gnome/desktop/wm/keybindings I tried to create those shortcuts writing ['Right'], ['Right'] and anyone works. I don't know why ['Up-Down'] are working, they even aren't specified in that place in dconfig. When I take a window with the mouse and I carry it to a side it doesn't fix as it use to fix before I get the problem, in the half of the screen. Another thing, I started getting this problem when I change the computer but I kept the harddrive. I'll appreciate any help guys
When you change the hardware of the computer, the OS needs to be reinstalled for it to work flawlessly. If you "kept" your harddrive, then most of the functionalities would work, but somthing configured specifically for your old hardware would not work with new one.
I suspect that the problem you described above falls in this category.