Sorry guys, but I like to reply to myself, to here is another message :
I've been testing this issue a little bit, and in fact the digital pad is working, but not like it should (it's not playable):
So when you are in "digital pad" everything's fine.
But when you select "analog pad", the sticks are working great, and the left digital arrow is working like expected.
I noticed after a few tries that the 3 others directions (up, right and down) are working if you press the button at a specific level.
The Sixaxis pad has "analog" digital buttons (lol) : even the normal buttons are pressure sensitive, and for these 3 it works only at (i'm guessing) half pressure of the button.
Once you found the correct intensity of pressure to apply it acts like a turbo button, because it's difficult to press always at the exact level of intensity.
So I'm supposing that when you activate analog mode for the joysticks, it's also enabled for the up, down and right buttons.
A fix in one of the next versions would be great ;)