The 50mm f/1.2 L won't focus right with any AF sensor on any 5D. I've tried it on 5Dc, 5DII and 5DIII (and 7D for that matter). My lens, even at the best AF adjustment setting (-20) it misses more often than it hits (stationary high-contrast target from tripod). I wouldn't exclude the possibility of my sample being sub-par, but if you decide to get one of these, make sure the shop has a good return policy. I'd actually recommend getting the Sigma 50mm f/1.4 instead.
Having said that, both the 35mm and 50mm focal lengths are useful for weddings, and the 35L is excellent.
Looks like you should have the lens sent in to be calibrated. Mine works OK on a 5DII with AFMA.