When I tested fill.asm, I found that no matter how many times I pressed the keyboard button in CPUEmulator, it just won't go to execute the code, not to mention paint the screen black.
D = M
It just won't go to BLACK. I downloaded the suite from the website, and I was using WINDOWS7 32-bit
The code snippet looks good.
The button on the screen with the keyboard icon is used to set keyboard focus to the simulated keyboard. Click on this button once and it should become highlighted and your PC's keyboard will be connected to the Keyboard component in the emulator. Now press and hold a key on your keyboard and its keycode should be read from 24576.
If I've misinterpreted your question and this is how you are using the keyboard, then there is most likely a problem elsewhere in your code. If you want to, you can email it to me and I'll take a look at it sometime tomorrow.