Currently, NXclient has some problems with handling the keyboard correctly on “newer” X-implementations (such as Fedora 10 and 11). Keys like the arrow keys or backspace are misinterpreted or don’t work at all.
A quick workaround to fix (at least most of) the keys
setxkbmap -model evdev -layout your_layout
on the server side.
for danes, this works a lot better
setxkbmap -model pc105 -layout dk