Please take a look at the Adobe document on Troubleshooting for Premiere Elements damaged projects to determine if any of the suggestions in it work for you.
Deletion of the Adobe Premiere Elements Prefs file (mentioned in the Adobe document) often remedies unexplained happening. But no guarantees.
Did you move, delete, or rename any files/folders linked to the project?
We will discuss the matter further after you run through the systematic Adobe document troubleshooting.
Thank you for responding. I had already gone through that particular document and did as instructed to troubleshoot on my own before I wrote the post. I've just gone through it again, (1,2, 5-8 as instructed) and the same problem exists. Since previous projects will open and I can create new projects, I'm thinking I just need to bite the bullet and start over again.
Although troublesome, the good news part is that you can open previous project and create new ones.
Was there anything different that went into this problem project that you might point to as a possible cause of the problem?
Source media, effects applied, size of project, etc. You seem to be working with AutoSave On in preferences. How do you have that set for numbers of snapshots and timing between snapshots?
Starting over is good choice in this one instance, but, if the problem happens again, then we need to dig deeper for possible cause.
We will be watching for your progress when you get a chance. Your follow up with details was much appreciated.