Problema MonthName(Month(Date())-1)

[JonaRock]

Hola NeoDani

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim nombremesanterior As String = ""
nombremesanterior = MonthName(Date.Now.Month) TextBox1.Text = nombremesanterior
End Sub

Con eso solucionas tu problema.