Kerbal Space Program

After I have played for several hours, KSP almost always crashes when I exit.

I either press Alt+F4, or the Quit item in the menu, and the game freezes with an eventual standard windows error dialog with the application not responding. I don't know if it's stuck doing something in a loop or what is happening. I've tried to wait to see if it eventually finishes, but doesn't seem like it.

I currently have some mods installed, but happened before I installed most of them as well.