easyCIS setup suggests the use of integrated security for database access. If you didn't provide user name and password on the setup screen, the default behaviour for setup is to use current users credentials to access the database. However easyCIS consists of several services and a web application running under Local System account. If you are getting this error, make sure MSSQL is set to enable Local System login.
easyCIS comes with a utility called CreateDatabase. It is being run as a part of the installation process. Its purpose is to create CISystem database on MSSQL server and to update it to current version with change scripts. This automated process is far from being error-prone and although effort has been made to make it as straightforward as possible, it may simply fail due to some sort of configuration error.
One such error I'm aware of is the implicit use of named pipes by sqlcmd.exe and its improper configuration on mssql express eddition databases. (see http://blog.mclaughlinsoftware.com/2009/05/16/fix-sql-server-2008-client/)
If you experience errors creating the initial database during setup, note that you may safely delete the database, correct the error and run the CreateDatabase.exe without the need to reinstall easyCIS.