After a reboot (killing X is not enough) things are mostly working:
+ screen rotation applet in the bottom bar works
+ arrow keys work in "desktop" and tetris (and mostly everywhere)
- arrow keys in sokoban don't work. They work but their effect is rotated by 90°
- in "screen setup" the effect of portrait/landscape is swaped

After some time (don't know how to reproduce) things go worse:
- screen rotation applet has no effect
- arrow keys' effect is rotated by 90° EVERYWHERE (tested sokoban, tetris and desktop)
- apps behave as if left-arrow was constantly pressed at an interval of about 1sec
- "screen setup" thinks we are in potrait mode (while we are in landscape actually) and trying to change it has no effect.

People pointed out this was a due to missing keymaps but is it really? The keys in question work mostly. The software must know about how to match key codes.

Where am I supposed to file this bug? GPE?