Cannot install silverlight 4 tools on visual studio 2010 sp1

I've installed Visual Studio 2010 (fresh install), then applied the SP1. Now I've tried to install the silverlight 4 tools, but i'm getting a strange error message :

"Visual Studio 2010 or Visual Web Developer Express 2010 or Visual Phone Developer Express 2010 that matches the language version of Silverlight Tools 4 must be installed before installation of Silverlight Tools can continue. Silverlight Tools is available in other languages at http://go.microsoft.com/fwlink/?LinkId=177432.

The Visual Web Developer feature for Visual Studio 2010 must be installed before installation can continue."

I've triple checked and there's no language conflict. Browsing the web, some guys have the same error, but there are some MSDN posts that say that with SP1 you don't need to install silverlight tools because they're already bundled with SP1, but that's not the case here, I don't have any project templates in VS for silverlight, and the tools aren't installed. Any ideas??