While creating a new Web Application through VS 2012, I was facing this compiler issue.
Error
Project 'WebApplication1' could not be opened because the Visual C# 2012 compiler could not be created. Error creating instance of managed object 'Microsoft.VisualStudio.CSharp.Services.Language.ManagedObjectFactory' (Error code is 0x80131513).
Solution
1. Open exe, VS2012 x86 Native Tools Command Prompt (Run as administrator).
Path: C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Microsoft Visual Studio 2012\Visual Studio Tools
2. Then run gacutil /u Microsoft.VisualStudio.CSharp.Services.Language.Interop
This will successfully uninstall the service from GAC, which was causing the problem.
Open the VS 12 again and start creating projects.....