I have a problem with Visual Studio 2008. When I installed vs2010 rc1 some strange error messages appeared when I opened a silverlight3 solution in vs2008, I told it not to show it again, but I remember it have some strange guid keys.
I have reinstalled everything and it keep showing no silverlight designer when I open a xaml, but the solution work well and I can execute it normally, but I have no xaml intellisense and preview (it just appears with black character as in notepad).
Thanks
I am using vs 2010 rc1, I did not got any strange error and it works for me as smooth but it crashes a browser lot for the web application.:( .. vs 2010 supports sl4.And you can see silverlight designer.
So please remove sl4 if you have installed and install it again.