VB6 - operation is not allowed when the object is open

but you never close the connection.

this must occur on the second hot of the code. Your connection scope is global so each time your code is hit you are using the same instance of it. The first time it runs through, you set the connection string and open the connection. The second time it runs the connection is still open (very bad).

Your connection should be at the lowest scope possible. That's why you will usually see it in a 'using' block. This makes the connection scope even lower that the function itself.

Always close connections
Always dispose of connections

These are't just guidelines, it's the law! :Þ

Hope that helps ^_^
Andy

EDIT: updated with code

Option Explicit
Public Report As New CrystalReport1

Public Function printReport()
     
     Dim strConnectionString As String
     Dim rs As ADODB.Recordset
     Dim strScript As String
 
     strConnectionString = "Provider=SQLOLEDB............"

     Using mvCn As New ADODB.Connection
        'mvCn does not exist outside of this block!
        mvCn.ConnectionString = strConnectionString
        mvCn.CommandTimeout = 0
        mvCn.CursorLocation = adUseClient
        mvCn.Open

        strScript = strScript & "SELECT * FROM employee" & vbCrLf

        Set rs = mvCn.Execute(strScript)
        mvCn.Close()
        'Always close before leaving scope.  This should happen anyway but it's always good to be sure
     End Using
     'That's it.  mvCn no longer exists.  When the code runs again mvCn will be a new instance

     Report.Database.SetDataSource rs
     Report.AutoSetUnboundFieldSource crBMTNameAndValue
    
     CRViewer1.ReportSource = Report
     CRViewer1.ViewReport
    
     Set Report = Nothing

End Function