Regarding the crashes (a560, ixus75):
The crash reasons are various exceptions, I suspect stack corruption/overflow (LR is okay, PC is not).
CHDK-shell doesn't pick up the correct dump file (as it was not adjusted to the new style build process used in trunk). This dump is located in platform/[camera]/sub/[fwver]/ and is named main.bin.dump. I'm not sure if the dump would say much more about the circumstances though.