From Rockford Lhotka's Expert C# 2008 and VB 2008 Business Objects books
I use cslacs.sln, so I don't have any trouble building csla. I don't know what cslacs.sln is for, so I'm not much help. If webmvc has anything to do with asp.net mvc, I do know that you have to install asp.net mvc before you can load an mvc project into visual studio.