This topic has been quiet for a long time but it was the only answer to mu IMMENSE frustration with 7D.
I have been through hell with brand new 7D body since day one (Oct.2012), it had and still has exactly the same problem other were mentioning: intermittent HEAVY front focus while showing green light confirmation in the WF.
The lenses affected are in the 17-50 2.8 range of any make: be it Canon`s original 17-55 or Sigma 17-50 or Tamron 17-50 anywhere between 10-30% of images end up useless with catastrophic front focus AF failure. It has nothing to do with AFMA, all lenses focus correctly - until camera occasionally goes wild. At medium to long distance the error can be measured in meters
not inches. Medium to low light conditions can 'improve" failure rate up to 50%!! I sent the camera back to Canon for check up almost straight out of the box, got it back the same with remark that "camera was within the specs" and since I had Sigma 17-50 2.8 OS at the time "it might not work correctly with Sigma." BTW that same Sigma worked flawlessly on my 40D and 50D...So much about canon`s support. So I sold Sigma and got canon 17-55 Is - only to get same if not worse results...
so I got Sigma lens again. Camera came with 2.0.3 software installed so I could not compare with older versions but it seems that downgrading to 2.0.0 or lower worked for someone here, right? Funny thing is that other lenses I have (50/1.4, 70-200/4 L IS, 85/1.8, 200/2.8 L, 18-55 kit lens ) work more or less fine, 18-55 3.5-5.6 cheapo kit lens being dead-on 99%
Also, I tried 3 brand new 7Ds (including mine) with 2.0.3 firmware - all three had exactly the same problem
. Any comment and suggestion would have been HIGHLY appreciated. How I can get and try to downgrade firmware and is there any risk associated with that? Thanks...
UPDATE: downloaded version 2.0.0 (would not go further than that) just waiting the comment is it safe to take this downgrade route.