The S key seems to be mapped to an incorrect value in XQuartz for me. I am running OS X 10.7.5 and XQuartz 2.7.4 (xorg-server 1.13.0). The problem also occurs in X11.app (XQuartz 2.6.5, xorg-server ...
I'm using an editor that requires X11 and for the most part it works well. I have many commands that use the Alt key and I like to navigate the menus this way as well, but the Alt key doesn't work ...