dvdxlr12

What do I do about this?

My problem is that I will save my work and get off for the night, but when I resume my work in the morning like this morning, my work is all messed up. I get this weird message and I have to keep clicking OK like over two dozen times. And after that I will load my project and it will be missing some things that I did to it last night. Does this make any sense? Like some of the terrain will be completely gone.