I've been working on this project for about a month and I just started receiving this message. Now I can't even save without generating this error. I'm sure there are some files it can't find. I made changes to the file structure when I first began (I took this over from a prior user) and I believe I've done some sort of damage. I change the order of the folders back to their original layout but that apparently did little good.
A clue: I have two topics with the red X next to them that are duplicates (in name) of two current topics. When I try to delete an Xed out (old) version I get the " . . . has encountered an error . . " message. This wasn't always the case, however. When I first noticed them last week and was able to delete. They're back and causing trouble.
So far, so good. The red-X topics did not show up when I opened the project and I’m able to make changes and save. I had made changes to the project structure in Windows Explorer.
You saved my bacon again, Mr. Grainge. Thanks!