_ascx is ambiguous in the namespace 'ASP'

Hello,
I know this is an old problem but unfortunately I haven't been able to resolve it using the suggested method and hence, this post. I created a UserControl that used throughout a web app. However, after a recent Windows update, that the "_ascx is ambiguous in the namespace 'ASP' error start occurring. I've added the ClassName to the @Control directive to no avail. Here's a sample of the code:
'UserControl HTML <%@ Control Language="vb" AutoEventWireup="false" CodeBehind="dlgMessageBox.ascx.vb" ClassName="dlgMessageBox" Inherits="Legitigant_WebApp.dlgMessageBox" %> 'ASPX page that utilizes UserControl <%@ Register Src="dlgMessageBox.ascx" TagName="dlgMessageBox" TagPrefix="uc3" %> ..... <uc3:dlgMessageBox ID="dlgMessageBox1" runat="server" OnMessageBoxSelected="OnSelectedMessageBox" ...