I have just installed the Nightly Build onto the 5D MkII. Can see the functions but when I press the button to go to shooting mode the error 'Error 30' comes up and tells me to either turn the camera off and back on or to remove the battery and put it back in. Only removing the battery and putting it back works, to get access to the functions again. Shooting seems impossible any which way. I take the card out and the Error 30 still appears when I press the shooting button. I tried reformatting the card in the camera but still it kept the Nightly Build. But in any case, card or no card, my camera seems affected. What is the best thing to do in this case?! :'(
And now it won't turn on at all without a card or with my alternate card (which I deleted all files from through card reader/macbook, and put Canon firmware file onto). It will turn on with my Magic Lantern card but immediately goes to shooting mode and gets the Error 30 stating also 'skipping module loading..'
Tried to include the log but it wouldn't publish here for some reason..
If you just remove ML files from card the cam won't be able to start because card is still bootable (something done during ML installation). Format card in cardreader to clean card. Read FAQ and installation guide.
Error 30 is caused by shutter failure, perhaps a worn or dirty shutter. I do not think it's related to Magic Lantern. And If it occurs also with no card in the camera, it's certain that it's not caused by ML.
I have a 50D that also shows error 30 sometimes. In my case, using manual exposure mode, and waiting 2 or 3 seconds after a shot before full pressing the shutter button again, is enough to avoid the error.
List of eos error codes and messages (http://cpn.canon-europe.com///content/education/infobank/camera_settings/eos_error_codes_and_messages.do) and if you do have a shutter issue then here is guide DIY: Canon 5D Mark II Shutter Replacement (http://mylesdunphy.com/2015/01/canon-5d-mark-ii-shutter-replacement/)