.NET 4 SDK corrupted? with Silverlight 4 Tools install

I installed Silverlight 4 and now my C# projects that use some of the new .NET 4 classes 开发者_运维问答like System.Threading.Parallel and System.Numerics.BigInteger don't appear to be present.

Have tried switching between selected frameworks in the project properties, and downloading and running repair on the .NET 4 SDK, but didn't resolve the issue.

Edit: Project act's like it's being compiled with .NET 3.5 SDK.

Reboot apparently fixed the issue after the repair.