When I tried to open a Silverlight project inside Visual Studio 2010, it failed with the following error message:
“The imported project "C:\Program Files\MSBuild\Microsoft\Expression\Blend\3.0\Silverlight\Microsoft.Expression.Blend.Silverlight.targets" was not found.”
When I tried to open the project on another machine it worked fine. So I realized that it had to be an installation issue. After comparing the two systems I noticed that the Blend 4.0 SDK wasn’t installed on one machine. After installing the SDK everything worked perfect.