Originally posted by Sorver Oh wow didn't realise that failure to turn off when changing lenses could do that not a common practice of mine either but fully possible it has been done.
The sd card was bought brand new before I went overseas so different sd card to the one I was using also a extreme pro.
As I posted factory reset and all seems to be good now so hopefully stays that way but at least if it doesn't I will have a few different things to try and be aware of.
Scooter gives some very good advice. With two camera bodies showing the exact same behavior, I'd look for what's in common. Or try to remember exactly what you did just before the freeze-up. Is there a sequence of actions that triggers the problem. I've had a few freeze-ups with my old K200D, but was never able to find out what caused it. But it was so infrequent over many years of use that it never really bothered me.
With my K-30 ( essentially the same as your K-50 ), I was messing around with extension tubes once and found a configuration that consistently caused it to freeze up. It turned out one of my old extension tubes was faulty, and it looked to the camera like an open contact. I posted the story on this forum. I don't think I've had the camera freeze up on me under normal use.
So it could be that there's something else that caused both cameras to freeze up. Now, one could argue that the cameras should be robust enough to handle external problems more gracefully, but a DSLR is a complicated piece of equipment, and it would
take years to test every possible configuration of settings with every possible lens ( faulty or not ). The cameras would never make it to the field.
If it does turn out that you have 2 bad camera bodies, that would be a bad string of luck.