Originally posted by candgpics I have read that battery/voltage issues may affect this and the battery (Pentax OEM) was fully charged.
That may suggest the battery was a bit over-charged, especially if it was put into the camera straight off the charger. Get a second battery and cycle them through the camera, always using the battery that was charged most recently last.
Another question - were you using a battery grip? Some of the third party ones have a reputation for causing strange camera problems, like lock-ups and other issues.
I'd also be curious to see the full EXIF of one of those 'double jumping' images. That will include some perhaps useful information about the camera state, including temperature, battery levels etc etc.