Big Business Client works with Sleep settings on your Mac to connect again to your Big Business Server on waking . This is handy, except when Server is not to be found.
If Server was shut off, or if you switched networks, or it has been too long in Sleep mode, Client may not connect again and try to Quit. Or, it may need to be Force Quit.
Choose Force Quit in the Apple menu, click Big Business Client, and click Force Quit.