if you want to log in as root you can either end your x session (in kde choose logout, end this session only) then login as root. the login manager doesn't present a choice for root, but you can type it in.
or better yet, press crtl+alt+F1 , (or any of F1-F6) then login as root, do your magic, type exit and crtl+alt+F7 to return to X.
on the permissions i'm not sure what's going on.
is the partition that /usr/share is on mounted readonly for some reason?