This happened to me near the end of a bike race I was shooting today. Did not happen on every shot afterwards. I was using the new 16-35L II lens. Happened on both cards in my MarkII, I switched over to see if it was the card, but doesn't appear to be unless both are going bad.
The only other thing is the battery was pretty low.
Tried the mirror lockup, didn't see any out of position blades, I tried it a couple of times. Probably best I send it in as it was not consistent. Some of the last shots I took were OK, and some had very faint streaks.
It does look like your shutter is about to blow. Definitely send it in to Canon. If you are sure of the acutation count, and it is that low, write a nice note telling them that even though the camera is out of warranty, you don't feel that the shutter should be failing at such low actuations. If the right person sees it, they may replace it for free since it has so few actuations. They did mine for free (15k actuations) but have charged others for it. Guess it depends on who processes it, how clean the body is (not abused) and how low the actuations.
I agree w/ the other posters. Don't use it, send it to Canon ASAP.. If you continue to use it, the shutter could come apart and do much more damage and that means even more $$$.
Just went through this with my MarkII this summer. I have about 66K at the time, and they knocked 20% off of what the replacement cost me. Just ask them. Do I get to call my Shutter count 4,500 now :-)
Whenever I see a blown shutter post it's from someone that has a 1D body. Makes one wonder if they have more shutter problems than the lower end bodies. I'd assume not.
1 Series bodies work harder in the mechanical sense. Fully automatic firearm vs single shot or semi-auto comes to mind.
Yes, do get that body into Canon Service ASAP...using the shutter in that mode may well fly apart and do damage to your sensor then your $2K body is really going to take a severe drop in value.
I'm on my third MKII body and never a problem; all obtained used with from 7K to 27K clicks but there have been several posts about early shutter failures.
I have not received the official word yet, but I'm blessed to have a Canon authorized repair shop nearby where I work. The guy who took a look at my photo & camera said there is a possibility it may not be the shutter, but to wait for his main repairman to go through it. I will get it back in a couple weeks. Stay tuned.
Free shutter would be nice, however my MarkII is not the "N", it's from one of the earliest batches sold to consumers right after they released it. I believe that was August of 2003.
:-)