Hello & welcome Mike !
In the CHDK video settings menu you can only set up the compression of the video, not the resolution or the framerate, you can either use a bitrate factor (0.25 - 3.0) or the quality setting (up to 99, this means max. quality), the settings overrides the cameras default video compression.
The default values in CHDK should be near to the original Canon ones (bitrate 1, quality = 84).
The flashing red "!" is a origin Canon indicator, it means that the video buffer runs out of memory soon, this is a indicator that the bitrate / quality setting is to high, the camera can't save the data stream fast enough to the card - use a lower setting, with a quality of > 98 you'll get up to 10 MB per s and more to save to the SD card !
