First, check to see if the anti-virus program might be interfering with the packing database process. Try temporarily disabling the anti-virus and launching the program.
Second, make sure all users have full permissions (read, write and modify) on the Essential Forms program and data folders.
Third, try to open the Essential Forms program in Safe Mode with Networking. It should pack the databases and open. If so, you can go into Configure>Preferences>Database tab and uncheck “pack new databases on next launch” and click Ok. Close Essential Forms, boot back into Windows normally and it should open fine.