The following are items to consider when getting a 6420 error when opening Medisoft:- Cumulative Security Update for ActiveX Killbits for Windows XP (KB2618451) This Microsoft update caused 6420 errors. Need to go to Control Panel, Add/Remove, sort by date, look for recent updates as of 12/2011 and remove this update. Reboot and Medisoft should open up. - Set Medisoft 14 icon to run in XP Compatibility mode with admin rights to resolve the 6420 error that happens when changing user rights in Windows 7. Turn off UAC, and Power Management on the network adapter (on the server and the workstations).Under Advanced System Settings, set Performance Otions to 'Adjust for best performance,' and confirm that sleep mode is disabled for the computer. - Is the server on?  Is Advantage running? - Check firewall settings; on the server, ads.exe (the Advantage database executable) needs to be allowed, and on the workstations, Medisoft and Office Hours and Revenue Management, as well as any other add-ons, need to be allowed. - Is the server's IP address static?  If it is dynamic, it could have changed recently, and if that happens while Advantage is running, then the workstations will not be able to discover the database.  Restarting Advantage is a quick, temporary fix, but if the IP remains dynamic, it will happen again. - Are the server and the workstation on the same network, and on the same subdomain (i.e., 192.168.1.x)? - Is the network connection between the two computers at least 100MBps?