On my A570 IS CHDK 1.2 runs nicely.
But when I use CHDK version 1.3 (rev. 3487) and take a picture, afterwards there is nothing anymore to see from CHDK: No OSD, no menu, ...
But it seems to continue to run in the background: When I press the button for <ALT>-mode, the canon-functions do not react anymore -- everything as if CHDK is running but not displaying anything.
Furthermore, I have the script [http://chdk.wikia.com/wiki/Manual_Exposure_Control_for_Video_Recording
]) loaded; when I am in the suspected <ALT>-mode and press the shutter button, the script displays itself and works and takes pictures and I can also quit it -- but this does not make CHDK to re-appear on the screen.
Only way to get it back is to switch of the camera and on again.
By the way, in the video mode there is not the problem. (But switching to video mode and taking a video after taking a picture does not bring CHDK back.)
I mention that I have version 1.3 installed on a 32 MB (yes, mega
byte)-SD-card, but that should not be the problem -- there is still plenty of space compared to the size of CHDK, and space for ca. 10 seconds of video or some pictures. (I cannot test with another card since I don't have one free and don't want the hazzle of swapping the CHDK-installations.)