I have been using CHDK for a year or so and I am now experimenting with ptpCamGui.
So far I have failed to get ptpCamGui to connect to a camera. I have tried two computers, three different cameras (A590is 1.00E, A590 101B, SX110 1.00B). In all cases, ptpCamGui waits for the camera and then resets, over and over. No error messages are generated.
libusb-win32 is installed and seems to be working for each camera. When a camera is attached to a USB port, Windows device manager lists the camera in the Imaging devices category with a warning that Windows "cannot load the device driver". This appears to be as intended.
Perhaps the camera is not in the correct state or I have not followed the necessary start up sequence. Can you suggest how I should proceed?