Pro freezing/not responding on the Program Window

I had this same problem with a computer and decided it must be the computer itself, so we purchased a new system and at first, I was having no problems. But, today, the old nemesis popped back up.

System: Lenovo ideacentre Y700

     Windows 10 Pro

     Ram: 16gb

     64-bit

Current version of Adobe CC

Problem: When editing, the video playing on the program monitor will suddenly freeze. I can still move the bar, select other videos, but my preview window will still show the frame that it froze on. I can save. I can drag and drop stuff, but can't preview anything. I cannot shut down Pro unless going through the task manager and ending the task.

This happens on video that has no special effects added to it, or on projects that are high-graphics. It doesn't seem to matter (this was the case with the older machine). This time, however, I had just finished editing with green screen and motion graphics and then opened up a brand new project, imported in some video (from the same camera with the same settings as I always work with) and dropped the clips onto a sequence and FREEZE. There's nothing special about this clip!

I've googled and searched for answers and found nothing. Things I've tried:
>Cleaning the cache
>Uninstalling and reinstalling Pro
>Shutting down all other programs

>moved clips onto the desktop or local drive (currently on an external drive - it hasn't made a difference where the clips are)

Any other ideas? Now that it's happening with a brand new computer, I'm wondering if it's an Adobe thing and not a hardware thing? What am I missing?