BC30560: 'default_aspx' is ambiguous in the namespace 'ASP'

Okay here is what I found after spending three days on this problem.

Finally I figured that if I removed all the projects from the solution except one (that was causing problem) I could isolated it to default.skin. The problem seemed to be very erratic because it started going away if I deleted certain lines from this file. However, this was not consistent and the problem came and went at random.

So after losing all hopes of fixing it in the code, I decided to try it another way. I changed the option of aspnet_compiler command from -prefix switch (a dll is created for each folder) to -o (all compiled ui is put in one dll), the problem went away!!!

It seems that the problem is due to some bug in the aspnet_compiler. It got triggered in this version somehow that I could not figure out.

I am thinking of moving to more stable asp.net 3.5SP1 (or maybe wait for asp.net 4.0) any suggestions?

I just solved this problem with the assistance following link: http://www.netomatix.com/development/usercontrols2.aspx

Add this on aspx or ascx page ClassName="MyModule"

   <%@ Control Language="vb" AutoEventWireup="false" CodeBehind="MyModule.ascx.vb" ClassName="MyModule" %>

I ran into this issue in consuming project when changing name/namespace of a library that consuming project referenced.

Issue is consuming project Bin folder has copy of DLL with each name/namespace name.

Deleting the consuming project Bin folder and rebuilding solved.