Help, lens problem...

I've had my 1D3, 24-70L, and 70-200/2.8L IS for over 2 years each, and they've been great. This month I sold my 70-200 and go the new 70-200/2.8L IS MkII and it's AMAZING!

I mainly leave that lens on my camera, then the other day I take it off and try to put on my 24-70L... it wont fit. It's almost like it's VERY tight after a bit of work I managed to get it attached and turned and locked. It took a lot of effort, but I was able to get the lens off. After doing this about 10 times, the lens was fine, attached and turned easy peasy (the new 70-200 would always fit perfectly.) I thought the problem was solved!

Today, I went to the zoo, took off my 24-70 and it came off nice and easy... I used the 70-200 for a couple hours then tried to change back to the 24-70 again... Sure enough, I couldn't get that sucker to turn. It pushed into the body but it took all my strength to get it on. Once again removing it and replacing it makes it smoother and smoother to turn.

I've looked at the threads and they seem fine. Has anybody heard of this before?

I don't have a Canon Service Centre anywhere with 2000km, so I will probably leave my 70-200 on and go down to a camera store tomorrow.

Thanks!

Check all the little screws on both the camera mount and the lens mount.
I'm betting you've got one that is just a bit loose and has back out just a little bit.
Or the mount on the lens has bent ever so slightly.

Sounds like a protruding screw.

Thanks guys I will have a look.
It's strange that it only happens after the 70-200 has been on for a while, and only the 24-70 is affected.

I had a 135L repaired after I dropped it on a hard tile floor. The mount got bent (same symptom as you are having). I looked at the mount with a loupe and compared to another lens. I couldn't see any damage. Still, it went on VERY stiff. Anyway.... Canon replaced the mount and it works fine.

I think what I am trying to say is that look very closely. It doesn't take much to have a problem such as you are having. Try tightening all the screws even if they look fine.

Thanks bohdank.
This sucks since the lens is super sharp, but out of warranty, and now I have a wedding coming up.
I will take it to a local camera shop to have a close look first.

Was yours under warranty?

Mine will be fine after moving it around and mounting and remounting it a few times (it loosens up properly). But after a day of using with my only other lens (the 70-200) then the 24-70 has the problem.