In CS6 on my MacBook Pro, I was all done editing several sequences and exported them via Media Encoder so that I could have video files to upload to the web. When I looked at the final video files that came out, 4 out of the 6 were missing the audio from the A1 track. I went back into the project file and found that the audio seemed to have disappeared from those particular sequences. The waveform no longer appears and it's grayed out. This is very strange since two of my sequences were fine and exported correctly.
I was able to double click the original audio source files in the project browser and the audio played fine from that. I took a clip from the source file and dragged it into the affected sequence and that particular clip's audio played fine too. The audio files are all .wav format.
I read other posts about similiar issues. I tried cleaning my media cache database. I also tried deleting preferences using Shift+Command when opening Premiere. I really don't want to have to go back and find all the audio clips and drag them in again!!