You may get the 'root element is missing' error message if some of the XML files from  %localappdata%\Red Gate\SQL Prompt 10 are corrupted.

To fix it, please try the following steps:

1. Remove the SQL Prompt 10 folder from %localappdata%\Red Gate\ and save it somewhere else

2. Reinstall SQL Prompt

3. If necessary, copy the custom style files and custom snippets over to the newly created SQL Prompt 10 folder respectively