I own two S5IS cameras, one with the 1.01A firmware, one with 1.01B firmware.
OK, that makes sense, I was wondering how you tested both
The crashing is probably caused either by the time it takes to save raw, or by the mere presence of the files.
You can try different prefixes/extensions for raw, which may solve the issue if the presence of the files is causing the problem. If it's the time, then you are out of luck.
If you know a bit of C and are up to mucking with the CHDK source, there's a few other things you could try. The first would be to force the raw to save outside of the DCIM tree. The second would be put in a delay loop in place of the raw saving, taking and try various times to see if it triggered the crash. You could also dump out the canon crash log, which might provide useful clues.
