I had a problem creating a Silverlight 4 or a WCF RIA Services project in VS 2010, and tried all possible installs and uninstalls but to no avail. I realized one needs to wait till April 15 for the official release of Silverlight 4, when all the tools will be updated.
So, in case you have a problem with opening or creating projects in Silverlight 4, don’t get frustrated trying to make things work; just wait till the official release, a few days from today.
This applies to WCF RIA Services as well as Silverlight tools.
