What do you mean "sync'd them from a usb cable?" Do you mean that you've loaded firmware onto the camera directly?
cdordoni is referring to using them in a multicam rig and triggering with the USB cable, after CHDK was successfully installed. This doesn't have anything to do with the install / boot method.
Right, I'd like to know where I might have gone wrong then. This is my first attempt at asking a digital camera to boot anything other than the manufacturers OS and I think I've followed the directions pretty closely.
Us too. This is pretty weird, because we don't know of any way you could mess up the install process to produce the symptoms described. In the ~8 years I've been involved with CHDK, nothing like this has been reported before. I'm not trying to shift the blame from CHDK or imply it didn't happen, it's just quite puzzling.
Random thought:
Were you using external power when cameras were bricked? A bad PSU could certainly brick a camera.
As I mentioned earlier, if you can measure the current draw when you try to boot one of the "bricked" cameras, that might tell us something.