Hello,
Thank you for your message.
First, you don't have to remove/uninstall Hosts to reduce the limit. You only have to remove the extra connections in your Viewer address book.
However, if you still get the message even after you removed the extra connections this might mean that your Viewer configuration file has been corrupted somehow. Just locate the file %appdata%/Remote Utilities Files/config_4.xml and delete it. This is on the Viewer computer. Then restart the Viewer - the file will get re-created and the error should go away. You might need to re-register your Viewer with the license again though.
Hope that helps.