VS 2010 RTM and Silverlight 4

I am not sure what is causing this. When I wanted to change silverlight target version from 3 to 4, I was getting the following error:

In order to fix this problem, you need to change registry entry from V3 to V4 at

x86

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\10.0\DesignerPlatforms\Silverlight

x64

HKLM\Software\Wow6432Node\Microsoft\VisualStudio\10.0\DesignerPlatforms\Silverlight