Thanks Bluetone. I did send the same question on to Charlie today. But I think I may have [yet once again] answered my own question. To wit: I frequently, in the midst of a project, do a 'save as' with the same name, just to make sure the latest version of what I'm doing overwrites all others. Carrara apparently does not like that idea. Here's my thinking: last night I lost a lot of work on a model. Today I re-built most all of it. I thoght that last night I had not saved often enough and mayhap the final [RAM]thought was too big. So today I saved frequently by simply doing a CTL_S. The thermometer bar flashed and 'saves' happened. When I wanted to close out, I once again did a 'save as' and got the 'error' message. Figuring that I was screwed once again, I closed with a 'don't save'. But knowing that a simple 'save' had been done merely seconds ago, I re-opened the file. Viola! Nothing was lost. So it seems that a 'save as' can only be done once to establish the identity of the file. After that, you get the 'error' message and a simpl;e 'save' is greyed out in the menu.