What happens is when you double click the entrant to finish them, IE tries to decide what to do with the scripted window. After several seconds, a pop-up warning window will open, and a status bar message will appear. In the meantime, IE is basically locked up. While we look for a permanent solution, here are a couple of "work-arounds".
First, you can reset the security settings in Internet Explorer. There is a video on resetting your security settings HERE
Or finally, you can use the finish time box, and click [Move Selected] for each entrant. But with larger fleets, or multiple fleets on a line, this would become a cumbersome process to say the least.
You may also need to check the settings again after any Windows or I.E. update, as the security settings have a tendency to revert after updates.