Thanks, Esther. I am already running v. 188.8.131.528. Is that the same version that you've linked to? It looks like it. I'll try a re-install and let you know what I get, but I'm guessing right now that this is the same version and therefore won't change the problem.
Hmm ... very strange. I have not changed anything, yet I can no longer reproduce the problem. Even as recently as 2 days ago I was consistently having to use Windows Task Manager to kill the application, and now it closes cleanly on its own. I've tested functions such as save, publish, research, and smart research to see if they have any effect (these are the most common functions that I use), but there seems to be no change in behavior. If I can reproduce the problem, I will troubleshoot and let you know what steps create the issue.