My DH, the database programmer, says that it sounds like Windows Explorer is crashing.
He says do the following:
1. Hit CTRL + ALT + Delete.
2. Click "Task Manager" button.
3. When that appears, choose File + New Task, then type "Explorer" and hit enter.
4. That should relaunch Windows Explorer.
*Note: Windows Explorer isn't the same thing as Internet Explorer.
He thinks that if you have a major issue, Windows Explorer might very well crash again after you do this. You might have to do a repair restore with your Windows software, or run a different brand of antivirus software (they are not all created equal) because it might pick up something your current software missed.