Campbell Scientific LNDB LoggerNet Database Software - Manual (Page 42)

LNDB
36
10. Troubleshooting
Database already opened by a different user
The "Database already opened by a different user" error can occur if Windows
UAC (User Account Control) is on, an application with standard rights
connects to the database first, and then a second application run as an
administrator attempts to connect. With UAC on, the SQL Server CE database
determines that the second application is being run by a different user. This
error can be seen with the LNDB Engine, because it always runs with certain
administrative rights.
To fix this problem, all connections to the database should be closed and then
the connection can be attempted again. If the first application that connects is
run with administrative rights, all other applications with or without
administrative rights can connect.