After migrating a website from vs2005 to vs2010 we get a build error - ASPPARSE: Object reference not set to an instance of an object.?

We have a VS2005 solution including two websites.

We converted the solution to VS2010 and changed all settings in IIS and in the config file to use .NET framework 4.0.

We removed the old assembly references in web.config file and added references to the new versions of the assemblies and here the problem comes: when we add a refererence to System.Design assembly in the web.config file the website does not build. The build via msbuild.exe results in the following error:

ASPNETCOMPILER : error ASPPARSE: Object reference not set to an instance of an object. [d:\DevSites\SolutionFolder\WebSite.metapro开发者_如何学Goj]

Does anyone have any suggestions why this happens? Thanks.

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We've solved it - after the removal of the browser definition file the problem disappeared