I installed a program called key-mon (code.google dot com/p/key-mon/) on my Ubuntu virtual machine and it won't display pressed keys (the way a lot of macintosh screencasts have a gray box with the pressed keys).
The site gave these requirements for running key-mon:

* Linux or equivalent (obviously, since I have Ubuntu)
* GTK+ (have the latest version of gtk+)
* pyGtk 2.0 (latest version of py-gtk2)
* DBUS (python-dbus) (latest version of dbus and python-dbus)
* Linux kernel event device interface (what is this?)

Since I have the other requirements, I assumed that something was wrong with my "kernel event device interface". I'm using the default (shipped) PS/2 keyboard. What is this, and how can I fix the problem?

Computer Info:
Asus U50F laptop with:
Ubuntu 9.10 (with VBox GuestAdditions installed) virtualized in Windows 7 Home Premium x86-64 (using Sun VirtualBox 3.6.1 r5938
Other OSes:
Ubuntu 10.04 LTS Beta 2 (on a separate virtual hard disk)
openSUSE 11.2 (on a third virtual hard disk)

I'll be happy to provide any other information necessary to solve this issue.