Many of the threads linked in this article are getting a bit old, but Jeff Bellune has some good comments on editing Camtasia footage (TechSmith CODEC) with PrPro: http://forums.adobe.com/thread/453044?tstart=0
Hope that something in there is helpful.
PS - while there is much other discussion, and a few OT aspects in some of the threads, the Replies by Jeff Bellune are the important ones.
Thanks Bill I will take a look.
Just remember that some of that material is rather old now.
Maybe we can persuade Jeff to do an update post on Camtasia footage into PrPro CS 6 (when he has the time, of course)?
Good luck, and I do not recall seeing such an anomaly before.