Hey,
I can't install the latest nightlys on 600D as well. I've tried several things, and it seems the autoexec.bin is broken.
Like told here, I overwrote the files from 2.3 stable with the nightly.
If I use the autoexec.bin from the nightly, the camera just won't start. Red LED is blinking like when reading a SD, but it doesn't stop, even when I remove the SD.
I have to completely remove the battery to make it stop.
But everything works fine if I use the autoexec.bin from 2.3 stable release - but then the ML-menu is the same like in stable, I don't get the new features like dual iso.