You might hit the error “Unknown Error” after uninstalled VS 11 Beta and .NET Framework 4.5 in the same machine that you have VS 2010. See the pictures below.
I uninstalled everything for VS 2010 and reinstall it to solve the problem. Somehow I realized when you uninstalled .NET Framework 4.5 Beta then .NET Framework 4 Extended and Client Profile will all be uninstalled. You can try to just install .NET Framework 4 back into your machine and see whether VS 2010 can work again.