After opening a UMR file, a *.umr~ file is created. I'm assuming this is just a working (unsaved) version of the changes the user's making at run-time. After closing the UMR editor, the *.umr~ file still exists. I believe this causes a problem. There have been several instances where I'd reopen a UMR (with the *.umr~ file still in the directory) and my class diagram isn't there anymore. The classes are still there, but no diagram. This is kind of annoying because there's no way to add a group of classes to a diagram, so I have to go one-by-one.

flanakin,
Do you mean that the "Design" portion of the window is blank, but on the right hand side the tree of the classes is all valid?

If you then close the diagram and erase the ~ file, and reopen your umr file, does the diagram correctly display? I will make the UML devs aware of this.