This new a570 test build is majorly broken.
The USB script still doesn't seem to work, but what's even worse, now all keypresses in alt mode execute not only CHDK's functions, but also the camera's own functions.
For example, if I press ALT and then MENU, I get the CHDK menu but the camera also enters it's own menu at the same time. And if I then press "arrow down" to navigate CHDK's menu, parts of the camera's own menu will be redrawn over the CHDK menu since the camera browses it's own menu as well.