I just discovered the N800's thumbboard the other day. It's normally triggered by pressing the "rocker" (center) button on the left side of the device when the cursor is inside of a text input. However, with the text inputs on my Flash apps, the rocker button doesn't do anything. I can't get the thumbboard to appear for any flash inputs; only the regular (stylus) keyboard.
Anyone have any suggestions on how to get the thumbboard to work under Flash?