I don't see anything wrong with posted code. May be you are overriding this selection in some other code. Here is a working example..

<asp:ScriptManager ID="ScriptManager1" runat="server" />
        <asp:UpdatePanel ID="UpdatePanel1"
            runat="server">
            <ContentTemplate>
                <asp:Button ID="btnDisplayDetails" runat="server" Text="Display Details" OnClick="btnDisplayDetails_Click" />
                <asp:MultiView ID="mv" runat="server">
                    <asp:View ID="view1" runat="server">
                        <asp:LinkButton ID="LinkButton1" runat="server">LinkButton</asp:LinkButton>
                    </asp:View>
                    <asp:View ID="view2" runat="server">
                        <asp:ImageButton ID="ImageButton1" runat="server" />
                    </asp:View>
                </asp:MultiView>
            </ContentTemplate>
        </asp:UpdatePanel>

    Protected Sub btnDisplayDetails_Click(ByVal sender As Object, ByVal e As EventArgs)

        Me.mv.SetActiveView(Me.view2)

    End Sub