Aug 16, 2011 09:02 AM|tonyhp1|LINK
This is something you may want to look into if you get this error after you PUBLISH your ASP.NET application from VS2010 (and not if you run them in VS2010 or just COPY all the files to your server manually).
Compiler Error Message CS0433 occurs when two different assemblies referenced in your application contain the same namespace and type, which produces ambiguity.
How could this happen only when we PUBLISH the website and not when you copy the files over physically or run them in VS2010 directly?
Please check this articule I found