Is there any chance you can borrow a different known good battery from a friend or in a shop?
FWIW, I seem to recall reading someone else posting about freshly charged batteries reading as empty as soon as they put them into their camera. You might want to try being creative with the search here, or with google - go to google, type in site:
The Largest Pentax Camera Forum and Review Site - PentaxForums.com Home < some search terms > and google's search may turn up some results not as easily found by the forum's search.
You could of course check the voltage on the batteries coming off of the charger (you may actually have a bad charger, as well), but I'd expect the batteries to fail under load more than just a simple voltage dropoff..
With the relative low usage on the batteries, and the fact that both are 'failing' at the same time, I'd be suspecting a camera problem as the more likely cause, but I'd do whatever I could to see if you could borrow a second charger and additional battery before sending it in.. good luck!