Solution: quit WordSmith Tools and enter again. If that fails, quit Windows and try again.
Or try logging. The idea of Logging is to find out what is causing a crash. It is designed for when WS5 gets only part of the way through some process. As it proceeds, it keeps adding messages to the log about what it has found & done. When it crashes, it can't add any more messages! So if you examine the log you can see where it was up to. At that point, you may see a text file name that it opened up. Examine that text, you might be able to see something strange about it, eg. it has got corrupted.