Hmm, I finished this game on N770 and did not notice anything. Right button is center button on the directional pad but I don't remember using it while playing this game. Oh wait, it was used for the rotation of the bones, right?

Someone on IRC said that touchscreen on N800 is too sensitive so there is some kind of filter in touchscreen kernel driver to smooth the data and filter out irregularities. Maybe some events get lost somehow in the process and scummvm is confused. Unfortunately I don't have n800 to check the difference. Try not to move the pen while pressing the button. Or if the right click work for this too use the key instead of touching the screen.