First of all, thanks to escho for returning 600D nightlies to life again! :-)
But... I own a 600D, and I've just tried to use the new build, Jun/10. I've deleted the config folder contents, of course. It loads fine... till I activate the dual_iso module. Then it refuses to load any more, if module is activated. Camera freezes in the first seconds (before even showing the free space in card) and I have to take out battery. And next time it wakes, of course, but, so that it was not cleanly shut down, not loading modules. Next time I tried to start it (so to load dual_iso), freezes again. No problem with some other modules, I didn't tried everyone, but did with advanced intervalometer, auto ETTR, file manager... and none of them gave problems.
Si, it seems to be only the dual_iso.mo the only to freeze my camera. So, I'm returning to previous nightly I was using (Apr/9, I think), which worked fine by now.
I don't know how could I give more information, till camera freezes before being able to do nothing when the module is tried to load at start. I there's something I can do to help, please, tell me.
BTW: I've post that also on the nightlies thread. Don't know which one is the most proper for this information. Feel free to delete any of both post if one of them is not in place, being redundant.