Well, here is how I think I have "fixed" it.
I decided I needed to nest my sequences. Instead of one big sequence, I am going to have multiple sequences and nest them.
To get around my "not responding message" I was able to keep the project working long enough to use the Project Manager to move the project ot a different folder and to trim the project.
Now, in the new location, I am creating three sequences -- by copying and pasting from the main sequence.
Then, tomorrow, I will nest them together.
Did some tests and already I am seeing an improvement in performance.
Are you defragmenting regularly? Copying a project to a new spot on the drive will create a new set of files that is not fragmented and would perform much better than the original files (if fragmented badly).
Yes, I do defragment regularly. And that was one of the first things I did when I had the performance problem. I like using Auslogics defragmenter -- it's extremely faster than the Windows defragmenter.
The good news is all is fine now that I use the Management program to move the project to a new folder (using the trim feature) and then deviding the project into three sequences. It's back to easy fast, editing as before --with no more "Not responding" messages.
Using the project manager also seems to get rid of lots of junk.