Hi!
No, automatic flash is disabled. I reset both camera firmware and CHDK settings from their menus, and also tried deleting the CFG file (in fact, I tried from a blank card with clean reinstall), but to no avail.
What I do is set "Subj. Dist. bracket value" to 2 and "Value factor (mm)" to 10 in "Extra photo operations->Bracketing in continuous mode", set the camera to continuous (I tried with and w/o AF), disable flash, and then press the shutter button.
The camera seems to take a shot, but it then crashes and switches off while not even retracting the lense. On switching the camera back on, no shots are stored on the memory card.
By the way, I just upgraded to build 425 form the 19th of June, and the problem persists.