eratic problem with effects preview

I have a problem when trying to preview an effect in stp2. The problem seems to occur after I have converted the clip to Mono. When I hit the Preview play button the meter registers only on the left side and then when stopped and started again it might spike the right channel to peak levels and distorts. It usually works if I use the space bar to start and stop but then it might go crazy also.
It doesn't seem to do it until I convert to Mono

I am having the same problem an a Mac Pro and an Imac

I had an issue with trying to update the OS to 10.5.6 on both machines then found the fix on Apple's site

Once I got the machines updated I still had the Prob. so I reinstalled Soundtrack on the IMac (threw the app. away from the Apps folder) Is that the way to delete in order to reinstall?

The problem still persists.

Please help

I remember having this problem a while back. Tossing preferences seemed to have fixed it.