I have tested Ultra Intervalometer on my A590IS.
This script - http://chdk.wikia.com/wiki/UBASIC/Scripts:_Ultra_Intervalometer
It seems that is not working, I know how to start script. Is there something more to do? I try in P mode, in M mode, in Av mode... what I need to do? I set 40sec exposure on the script, press the shutter button to start the script, then take a picture, but the exposure is what is set ot M mode, or what camera decided to be in P/Av mode, can't start the 40sec exposure.
Please help me, I need this script very much. I have tested other script that works, but is with some EV steps settings, cant guess what will be the exposure time with it. :'(