Going from CS 6 to CS 5.5-Audio not stereo in CS 5.5. It was in Cs 6

I have both Premiere Pro CS 6 and CS 5.5 on my computer. 

I would prefer to work in CS 6.

The person I am doing work for only has CS 5.5

I know I can open up a CS 6 project in CS 5.5, so thats not the problem.

I built a little test project on CS 6 with 3 clips of it, Video and Audio for a test. All of my Audio was playing in Stereo (Left and Right Track) in CS 6. I saved it.

I then opened up my CS 5.5 and went to File ----- Open ----- and went to the file I made in CS 6 and it opened up fine in CS 5. 5

One problem. In CS 5.5, the audio is only coming out of 1 speaker (1 channel) where it was coming out of both in CS 6.

Why is this happening and how can I fix it?

Thanks in advance