CS0234 Error on runtime, for classes in the same assembly
<p>We have an ASP.NET 4 Web Application Project. This project contains a number of pages. After having made some changes I get an error at runtime (ASP.NET Compile time) that this or that namespace cannot be found.</p>

<p>At design time (in Visual Studio 2010) there is no problem for Intellisense to see these namespaces and classes, which are in the project assembly themselves. And there is no problems at compile time in Visual Studio either.</p>
