Busy when i use the flash.

You either have a overheating or a recycle(recharging) problem with the flash. If it is under warranty send it back to Canon, if not I would suggest on investing in an external flash which is MUCH better for wedding photography.

Use a card reader instead of the camera from now on.

Try the camera after each step and look for any difference,
First reset the camera to the factory default settings.
Format the memory card in the camera(use the cameras format function).
Try another memory card.
The next step would be to upgrade the firmware.

Hope these fix the problem.
GL

i JUST had this problem with my EF70-200mm f/2.8 L IS II USM..
i was shocked at the time...but i did this to get it working again

1) turn off and on = doesn't work
2) turned off everything, removed ext. flash, battery compartment, batteries, unmount lens...reseend everything back in, turned on and it went away

Could be a card problem. How large is the card? Is it at least a class 4? Is it already full of pictures that need to be downloaded to make room? Has it ever been formatted in the camera?(This will erase it so download any pics first)

Are you trying to use the flash when you are having the problem? Were you taking a lot of pictures with flash when the problem started? Rapid pictures with flash can melt the flash and capacitors in the camera. Also, a single drop of water rolling around inside the camera in the right place can do things like that. You can try taking pictures in bright sunlight so the camera will not try to use the flash and see if it will work normally, If it does than something is probably fried in the flash system. Bad thing is that if you smelled smoke something is most likely already fried and will have to be repaired by canon. Canons quality has been going down hill for several years now and they have a lot of quality problems. If the camera has been used very little, has never been abused, dropped or wet and not far out of warranty, try using google to see if this is a common problem and call canon and try to get them to repair it for free. If all else fails threaten to replace it with a Nikon assume pay to have barely used camera fixed.

It can be that your batteries are low and takes longer to charge the flash... It can also be that your memory card is a slow on. If the red processing light on the back of the camera is staying on a long time, it means the camera is having trouble feeding the picture to the card... You might try decreasing the picture quality a little...

I believe your camera comes with a 90 day manufacturer's warranty. I would goto Canon's website as soon as possible.

Good luck!

I Can Fix It

I just called Canon because I was having the same problem. They suggested putting the camera in the sports mode. The reason it flashes busy is because there is a buffer period after taking pictures where the camera needs to store the information to the disk or if using a flash, then the flash needs to recharge. If you have plenty of natural light, then the full auto (the green square) mode can be selected because the flash won't have to recharge. If you are using the portait mode, then you will have to wait for the buffer period for the flash to recharge and the information to be stored to the disk.