usb arduino + director + multiple push buttons


i am trying to connect the arduino board over usb to director. i tried this code by wilson and i am using the serialXtra by geoff smith.

the examples work fine on the board, but somehow i get strange results inside director: when i push the first button, which is connected to pin3, then i get director not to read the H (H for high, and L for low) - when i push the second button which is connected to pin4 then director reads an H at this location. if i now push BOTH buttons, then director reads also an H for pin 3.

as i have not so much idea about electricity flows (just started) here the image of the wiring, maybe there is something wrong ? (i am using two 10kOhm resistors)

any help would be appriciated!

all the best