Which Canon firmware does your s5is have ? This would be 101a or 101b.
Which CHDK build are your using. The latest stable builds are here http://mighty-hoernsche.de/
You can also try the development builds at http://mighty-hoernsche.de/trunk/
But let us know which one you were using first.
When you say "extra camera options" what exactly are your referring to ? Do you mean the "Extra Photo Operations" part of the CHDK menu ?
Other things you can try:
Remove the CHDK configuration file. This will be either CCHDK.CFG (for stable builds) or CCHDK2.CFG (for development builds)
Get a romlog from the crash. See this wiki page http://chdk.wikia.com/wiki/Debugging#Camera_crash_logs_.28romlog.29
This may help us debug the problem.
Try to find out if the crash always happens, or depends on some camera state. For example, if you access the CHDK menu in playback mode, or in different shooting modes.