K5 playback glitch

Been noticing recently my K5 will sometimes refuse to go into playback after I've shot some images. Fixing it normally just requires flipping it off and on again but it is a little irritating. Haven't worked out if it happens more often any any particular circumstances yet.

Has anyone else suffered from this?

Maybe it's busy writing the images to the card? Or, if they are long exposures, maybe it's busy doing the dark frame subtraction?

When I've noticed it I've always checked to make sure the activity light has stopped flashing before trying again but even after waiting a while it still won't go into playback. It isn't totally wedged though as I can carry on shooting.

Not long exposures either, though I do shoot RAW+JPEG and have auto review turned off.

So it happened again at the weekend while I was at the Leuchars Airshow. I didn't have much time to investigate as I was concentrating on the display obviously but I did notice that it wasn't just the playback that was unresponsive but anything that required interaction with the rear screen. So Info, Menu, Drive Mode etc all would not display. However the camera would still shoot and the edials still function.

I also found if I left it and let it go to sleep when I woke it again everything worked.

On the other hand I also got a total lock up which I've only seen once before at the previous year's airshow. This time the AF indicator was on in the viewfinder and the camera was totally unresponsive. I had to pull the battery out to reset it.

I got my K5 quite soon after release so it could be some early manufacturing run weirdness.