A few times, our website has gone down throwing the following exception:

System.InvalidOperationException: ExecuteReader: Connection property has not been initialized. at System.Data.SqlClient.SqlCommand.ValidateCommand(S tring method, Boolean executing) at System.Data.SqlClient.SqlCommand.ExecuteReader(Com mandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream) at System.Data.SqlClient.SqlCommand.ExecuteReader(Com mandBehavior behavior) at subibl.DBUtil.ExecuteSP(Object[,] arr, String spName, SqlConnection cn)

where the ExecuteSP function looks like this:

Public Shared Function ExecuteSP(ByVal arr(,) As Object, ByVal spName As String, ByVal cn As SqlConnection)
        Dim cmd As New SqlCommand(spName, cn)
        Dim reader As SqlDataReader
        Dim i, j As Integer
        Try
            cmd.CommandType = CommandType.StoredProcedure
            For i = 0 To arr.GetUpperBound(0)
                cmd.Parameters.Add(arr(i, 0), arr(i, 1))
            Next
            reader = cmd.ExecuteReader(CommandBehavior.CloseConnection)
            Return reader
            cmd = Nothing
            reader = Nothing
        Catch ex As Exception
            System.Web.HttpContext.Current.Response.Write(ex.T oString)
            System.Web.HttpContext.Current.Response.End()
        End Try
    End Function

Obviously, there is some kind of connection problem to the SQL server. The strange thing is that it occurs without us having done anything, and a few minutes later, perhaps 5-10 minutes, it's up and running again, all by itself. We have checked the event viewer and error logs for clues but nothing.

Any suggestions what can be causing this problem?