Update... I guess I spoke too soon... 
The Face Detect OFF worked for a short time, but now the chdk menu is blanking out again anyway...
I have the touch icons turned off as well, but this blanking menu seams related to motion in the cameras field of view more than other menu or osd items...
Ok, now i can reproduce this - it's because the camera remembers the state of the display button (the OSD icons state), if this is OFF the OSD icons disappear after 5-10 seconds.
So you only have to enabled the OSD by pressing the DISP button - when OSD is visible, the cam remembers this...
The "touch button behaviour" (CHDK menu get's partially cleared when half-pressing the up/down/left/right buttons) is still not dissolved...