Severe performance issue when exiting to main menu

My computer experiences some performance issues after playing for a while. I start losing framerate during the game. The performance issues are sometimes somewhat mitigated while time is paused. When it gets really bad, exiting to the main menu causes the game to hang. Usually, this means I have to wait 5-10 seconds for the menu to come up. But this last time it was way worse. After waiting for a while, I try Ctrl-Alt-Del. The screen goes black, and then a dialog box comes up saying the operating system can't bring up the Task Manager/Login menu. I hit OK, then the screen goes black again, then my monitors say they're not receiving a signal and shut off. All with the music still playing. I had to hard reset my computer.

The Not-So Great Cosmos Cycle 64.sav