I have just finished saving 12 different configuration drawings of a sheetmetal vat I did up yesterday. I noticed everytime I saved the new drawing I was shown this message.

I pressed yes on each save without thinking too much about it. But now when I open each drawing I am shown this error message.

When the drawing finally loads, none of the sheets are responding. The drawing does not change - it is just the last sheet that I had open. I can't click on it or select anything. I have tried ALT Q to refresh, saving it as a different filename and saving it is a PDF. When I open the PDF the dimension are there, but the actual assembly or part is missing.

Does anyone know what may have caused this, and what I can do to open my drawings properly again?