1. Close the QSAR Toolbox
2. Locate the .plugin.config file containing the profiler xml
3. Back it up
4. Open it with a text editor (e.g. Notepad)
5. Replace all the occurrences of "<Family>Unknown</Family>" with "<Family>M</Family>"
6. Save it
7. Start the QSAR Toolbox and verify that you can now open the corrected scheme.