'd' key doesn't work in VNC viewer on Ubuntu 11.04
This is because 'd' key is assigned to "show desktop ( minimize all of the windows )" shortcut key by default.
1. Install gconf-editor.
$ sudo apt-get install gconf-editor
2. Modify key-biding of "show desktop" to something different.
It is located at apps->metacity->global keybidins->show desktop.