Hi thesteved111,
The question that comes first is, what's changed from where it worked previously?

To get a clearer picture of what you have and what's going on, members will need to see a diagnostic file, info on your media and a screenshot of the Edit workspace - to show us what you're doing and looking at?

See the guides, Part A, B, E & F and J.
Link: http://forum.cyberlink.com/forum/posts/list/45453.page

Here are a few guesses to check out:
Shadow edit files are being produced, slows the computer and you're editing before completion.
Preview player settings are too high.
Bitrate of the video is high
Video format is problematic, for example, avi (with a proprietary codec) rather than mp4.
GPU driver is out of date.
GPU is integrated or lower capable or needs to be software allocated.

As you can see, a wide number of guesses. If you provide the data requested, members may be able to assist you further.

Dafydd