Why would CHDK come with this enabled?
It doesn't. "delayed single shot" is the title of some example scripts that come with CHDK. You must have selected this yourself at some point.
If you are in alt mode, pressing the shutter runs the currently selected script. If you want to run a different script, select it. If you just want to shoot, leave alt mode.
If you are encountering the problem when not in alt mode, then it's unrelated to the fact you have this script selected.
Another thing that can cause the camera to appear to lock up after a shot is the Canon automatic dark frame. This should only happen for long exposures (> a few seconds), and the time the camera is locked up is equal to the exposure time.