1. Open Terminal in Applications > Utilities > Terminal

2. Type the following (exactly), or copy/paste:

sudo rm ~/Library/Application\ Support/Sword

3. Enter your account password at the prompt (you won't see any characters appear, but this is normal in Terminal).

4. Try MacSword again.

(Explanation: The error appears to be corrupt index files. The Terminal command is a fast way to remove the folder where those indexes would be. To see the same files in Finder, look in your Home Folder, and navigate to Library > Application Support. You should able to find a folder named "Sword" and another named "MacSword". The index files stored in the Sword folder can become corrupt under certain circumstances (such as having used MacSword 1 in the past and not re-creating the index files when upgrading to 2).