What do your code look like? Because just adding the dll:s and starting does not produce an error. Here is a sample code I created in VS2005, website:
Imports VisualCron
Imports VisualCronAPI
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim c As New Client
Dim conn As New Connection
conn.ConnectionType = Connection.ConnectionT.Local
conn.UserName = "admin"
Dim s As Server = c.Connect(conn)
lblNoJobs.Text = "Number of Jobs: " & s.Jobs.GetAll.Count.ToString
End Sub
End Class