I'm so glad I found a solution to open what I thought was a corrupt old DP project that refused to open. It's from 10 years ago.
So, every time I double clicked on it, DP kept telling me>
An error occurred while reading from the disk.
Project "xxxxx (with the full file pathway)" was not loaded.
Unreadable data was encountered while opening the file
I tried all of the following, and nothing worked>
- The Load command, while it showed me the project's chunks, it refused to load them as well.
- Safe-opening didn't help
- Deleted audio/Analysis files and still didn't open
- Compressed/decompressed full folder to no avail.
- Copied the project to my office computer, and it gave me the same error.
THEN, I tried opening it with DP9.02 instead of (9.51 or 9.52), and now it happily opens

It didn't find ANY of the old Waves plugin versions (even though I have the Mercury bundle), but I don't care. I'll be redoing most of it anyway.
Then I saved it normally in 9.02, and it opens fine in my main computer with 9.52.
Phew!
I wonder why? What can cause a project to be unreadable by the newest versions and readable by a slightly older one?
So it seems a good idea to always keep an old DP version installed, because this troubleshooting step was the last resort I could think of to rescue what I thought was lost!