So I thought I would update this post
After a one-hour conversation with Apple tech (in which he had to consult with a supervisor a couple of times) we assertained that because I have immigrated from many Mac machines and programes to my current Macbook Pro (late 2011) there are several third-party video componets in the Library folder for Quicktime. I had three Canon, four Flip4Mac, and one Perian component in the folder.
We took them all out and saved them to the desktop (or empty trash folder), restarted the macbook. At that point Quicktime said it could not open the video. We began replacing the components one by one, restarting the machine every time (very important). When one of the components worked (in my case Perian), I tossed the rest to avoid the clutter; now sound and video is no longer jerking or cutting in and out.
So the path to the Library files is GO > COMPUTER > MACINTOSH HD > LIBRARY > QUICKTIME.
The tech also said that Quicktime fhas been tweaked in the new OS 10.8.2 update. All I can tell you is that after we cleared the cache of extraneous components in the Library folder for Quicktime, and that was before I updated the software, everything is skoocum.
So, if you are a long-time Mac user you may have the same issue I had. I hope this helps someone out there.
