Multiple logons of the same user can create a security risk, hence there is an option to prevent/enable multiple logons.
 Under the View tab click ClinicOffice Settings
 Click the Global Settings tab
 Under the Advanced Settings header, you have the option to tick/untick “Allow multiple logons for the same user”
If you untick this option then when a user logs on to a second computer, he will automatically be logged off from the previous computer. The benefit of this is that it potentially stops someone accidentally leaving themselves logged in more than one place.