1st, Read Bill Hunt on Audio Conforming http://forums.adobe.com/thread/726693
2nd, AVI is a wrapper... what is inside YOUR wrapper?
Codec & Format information, with 2 links inside for you to read http://forums.adobe.com/thread/1270588
Report back with the codec details of your file, use the programs below... A screen shot works well to SHOW people what you are doing
http://forums.adobe.com/thread/592070?tstart=30 for screen shot instructions
Free programs to get file information for PC/Mac http://mediaarea.net/en/MediaInfo/Download
What computer operating system is your Premiere Elements 9.0/9.0.1 running on?
Does the video from the Pentax K5ll play back video and audio on the computer with a computer player? I know that you said it plays sound on your TV from the camera.
From what I have read, your camera is recording with MotionJPEG video compression and uses a .avi file extension. The audio is mono but I am not sure of the audio compression. The typical scenario with MotionJPEG.avi is in the video compression. Did a utility come with the camera? If so, this utility might supply missing codecs. Please run your video through the free gspot utility which should tell us if we are dealing with a missing audio codec situation.
What is your camera setting: 1920 x 1080, 1280 x 720, or 640 x 480?
We will be watching for further details and may have more questions later.