Comment 9 for bug 775590

That confirms Manfred Hampl's suspicion. In addition to changing karmic to natty in the last line of /etc/apt/sources.list, I recommend you also comment out the line right before that (the one that says jaunty), by putting a # character in front of it. Please see if those changes make a difference, and whether or not they do, please post again to report what happened.