During my shoot on Tuesday, my Canon EOS Rebel T3i 600D stopped firing until I took the battery out & put it back in after a few minutes. Is this a symptom of a serious problem?

It's probably only serious if it continues to happen. Can also be caused by by poor connection or dirty contacts on lens.

Quick troubleshooting steps

1 Turn camera off for 15 sec then on
2. Turn camera off,remove battery or battery grip. wait 15 sec, replace and turn back on. Try fresh batteries.
3. Turn camera off remove and reattach lens, turn back on.
4. Turn camera off remove lens, Clean lens and camera contacts with an eraser. Be careful not to get eraser dust in the mirror box. Turn back on.

Those should fix 98% of problems. If not it's probably repair time.

I concur - it's not a trend until it's a trend. Aside from removing the battery, look in the manual to find the clock battery (a smaller button battery to keep the clock somewhat in time while the camera is off), and remove/wait/reinsert this battery (if not outright replacing it - cheap insurance to rule out a simple thing). Are you using Canon-official batteries? If not, now's a good time to make sure you have at least one and see if the problem goes away when you use that one.
I'd not expect the lens contacts to be an issue with an outright freeze - for that I'd expect to see an error message on the back of the camera.
If it continues after these various troubleshooting steps, it's time for a trip back to Canon. It's easy to do and you can start the process online, which should help make sure you send it to a facility that's got capacity to handle the repair.

Thanks everyone

My first thought was buffer overload. That model is very slow to recover. http://www.imaging-resource.com/PRODS/T3I/T3IA6.HTM

Similar symptoms with one of my camera/lens combinations -- aperture flex cable in the lens was cracked and finally broke.

Very popular type of repair part on Ebay so it happens a lot.


Try using a different lens and see how it behaves.

Only if it happens repeatedly.

The fact is that DSLRs are computers with an operating system and software, and those have bugs that cause crashes from time to time. It's happened to me with my first DSLR, a Canon D30 back in 2002 or thereabouts; again with a Canon D5 (original), and while it hasn't happened with my newest DSLR pre Magic Lantern hack, it has happened since. But only once.

One thing you might consider is making sure you reformat the memory card in the camera rather than erase pictures or format on your computer. One of my earlier cameras would freeze up sometimes due to formatting errors introduced by erasing or formatting in computer.

I have had the same thing happen about once a year.  I did the same thing.  Turn off the camera, take out the battery and put it back in.
It does not seem to be anything to worry about.  This has happened with different camera models.

ive had a few camera freezes, but saw something on another photo forum. they talked about the memory going bad. i put a new card in, the problem hasnt happened since. i replace my memory for newer faster chips as well.

also another symptom i was having, my pop up flash wouldnt pop up when i pressed the button. it would make clicking sounds like the latch was being activated but it wouldnt pop up. the new memory cured that too.