About 30 minutes before heading out for an important day of shooting, while taking test shots to clean the sensor, my 5dmk2 froze on me. Here is exactly what happened:1) took a 10 second exposure at f22 at a blank wall to find dust 2) used the "clean sensor" tool on camera to clean the sensor (swab) 3) repeated 3 times until ... 4) when taking the next test shot, the shutter stuck open.5) After not hearing the shutter close after about 1 minute, I tried pressing a variety of buttons - nothing was responding. I then turned the camera off and on. While doing this, I heard the mirror flip back to it's normal position.6) After this, the menu system at the back worked, but the camera was otherwise unresponsive. Pressing the shutter half way would not activate AF, aperture and shutter speed could not be changed. There was no error messages displayed.7) I then turned the camera off and removed the battery, allowing it to sit for a couple of minutes.8) Adding the battery back in, I turned it on and everything was back to normal.Has anyone experienced this before?

... and every once in a while a cosmic particle flips a bit the wrong way, and you need to reboot. KP

Weird.Is there some sort of Canon bugtracker? Or at least an e-mail address to let them know about this kind of thing, so they can update in future firmwares? Today I found that the review screen wasn't coming up after each shot... despite it being set for 4 seconds...

Why the ten second exposure for the dust test? I don't think that shutter speed has anything to do with this. Just set the lens to the smallest aperture and fire away. If you need a ten second exposure, I suggest you turn on a few lights! -- Dick Thomas Kalamazoo, MI

Graham_Ashfordwrote:1) took a 10 second exposure at f22 at a blank wall to find dust 2) used the "clean sensor" tool on camera to clean the sensor (swab) 3) repeated 3 times until ... 4) when taking the next test shot, the shutter stuck open. 5) After not hearing the shutter close after about 1 minute, I tried pressing a variety of buttons - nothing was responding. I then turned the camera off and on. While doing this, I heard the mirror flip back to it's normal position.I don't understand, when you are done selecting from the menu and manually cleaning the sensor, you need to turn the camera off for the shutter to close and the mirror to come back down. How can it be you didn't shut it off until the end of step 5?

... absolutely not ... if I did not turn off the camera after the sensor clearning it would not fire in the first place.

A 10 second exposure allows me to provide sufficient movement so that I do not confuse dust spot on the image with, say, an in focus "blob" on my wall.

Ken Phillipswrote:... and every once in a while a cosmic particle flips a bit the wrong way, and you need to reboot. KPI agree that "once" is not a trend, but it's a concern. I spent the amount of money I did on this camera for a variety of reasons - one of them was reliability. I simply won't be able to keep a camera I can't depend on.I'll be talking to canon about this, but I wanted to check if I was the only one that this has happened to (looks like I am). Thanks for your replies.Cheers, Graham

I've had something similar happen to each DSLR I've owned.Like the hiccups, they may occur from time to time. If they occur with any frequency or regularity, then I'd consider consulting a doctor.