Unity crashes when quitting

Hi all. I've been getting a problem recently with Unity. If I've been working on a project for anymore than maybe a half hour or so, when I go to quit Unity, make a new project or open a different one, it crashes. It just hangs so I have to open the task manager and force quit it. Anyone else getting this? Seems to be happening since I've upgraded to the latest version. It's happened at some point with any project I've been working on so it's not a specific project problem.

It's not a major hassle, I can still save and everything so I haven't lost any work. And it's only when the project has been open for a while, so when I restart it I can still create new projects or load others. It's just annoying. I'm running Windows 7 and never had any problems like this until the past week or so.