SigmaStudio+ locks up

When I import a SS 4.6 design, I am able to edit and save, but when I re-open the project, SS+ locks up. It's a brick, completely unresponsive. While editing just after importing, I find it's rather sluggish to navigate, and sometimes I have to wait a while for the next screen to load. While waiting, SS+ is unresponsive. However, after re-opening my project, when I try to click into my design, it locks up and doesn't come back. (I let it sit at least an hour.)

software

sigmastudio+ 2.0.0

2.0 (Update 1) b8389 rev29218