I'll be brief here, but hopefully this helps. If not post more and I'll try to help.
1 - post some more information about what version you're using, what platform, etc.
2 - the audio mixer automation functions differently from the track automation. It's kind of weird I know, but that's the way it is. A lot of people get confused on this issue.
Going back, adjusting the View of the Track Keyframes helped. Obviously, something else is not working. Based on Dennis' comments, I wonder if Adobe has changed how the Audio Mixer works in CS4+. I only have PrPro 2.0, so I cannot even check, but I think that the playing field might have shifted in later versions. What version are you working in? I have a feeling that what I might tell you will be moot, and that someone else will need to chime-in, like Dennis.
I'm using CS4... I am using the audio mixer exactly how the "Premiere Help" instructions from the drop down menu told me to.
I'm going to start a new project and see if the mixer works properly. Again, the mixer was working perfectly at the start of the project