What gives, anyone experiencing this, got new batteries legit, new cards 95mb class 10 sandisk 32gb, all was working good till yesterday. During prep switching rapidly on and off all morning 3 hours no problem then later on during mingling hour, happening all the time all of a sudden.

No, but i've seen "movie has stopped recording automatically' several times . . . assuming card write issues, but the cards i use are plenty fast.

We had that issue with slower cards.

Since it stopped having trouble for a stretch, I'd try to figure out if it was batteries or cards since they change during the day. Or maybe the battery pack, if you use one, since you seem to saying you had trouble during the parts of the day when you were moving, and not during the ceremony when the camera would be steady on a tripod (?)

Mm thanks guys it must be the batteries then, but it was hot yesterday...

Not necessarily batteries... sometime that problem is from taking a card from one camera and using it another. I started formatting my cards every time I put them in, and in the 3 1/2 years since I have not had it happen again.

Yes, cards *must* be formatted in the camera, don't erase files using a pc/mac.

You mentioned new cards - are you sure they're not counterfeit? There are a lot of bad cards out there, it really pays to buy cards from larger shops. I don't know of a way to distinguish the counterfeits, but if you don't seem to be getting the performance expected out of a new card it's possible that it might be corrupt or counterfeit.

I have used class 10 SD cards on my 550D and now the 70D. The Transcend class 1 UHS Class 10 cards are rated at 300x and so far have been able to accept the 70D's 'all I' video recordings which often peak at over 80mb/s. Currently I am using these as Micro SDHC cards because they can fit in my Galaxy S 10.5 for on location viewing.
Could these interruptions also be as a result of overheating? I know that the 550Ds suffered in higher temperatures when asked to display video for long times on the LCD viewfinder. This was owing to the screen, causing the sensor, located just behind the screen becoming overheated.

Not necessarily batteries... sometime that problem is from taking a card from one camera and using it another. I started formatting my cards every time I put them in, and in the 3 1/2 years since I have not had it happen again.
Ha good shout i will try keeping the same cards in camera. cheers

Tried out Charles method and worked well yesterday, no switching off in heat as well. So going to use the same cards in the same cameras and then pop in the new card then format again for every card going into the camera, rather than just start shooting even though it has been formatted.. This method seems good thanks Charles.