I\'m trying to configure Visual Studio 2012 to allow me to step into ASP.NET MVC 4.0 source code. (System.Web.Mvc.dll). I\'ve followed SymbolSource\'s recommend
Let me start with that ReSharper provides a handy dialog to step in the code at any time:

So you get the following code screen if you drill to the source code:

But I became curious to accomplish this by hand. I started with proper pdb configuration:

After that I got the following error:

Next I copied the C:\Users\Andrew\AppData\Local\Temp\SymbolCache\MicrosoftPublicSymbols\System.Web.pdb\CA49C4332DE847FA967F58AFF370B70E1\System.Web.pdb to C:\Users\Andrew\AppData\Local\Temp\SymbolCache\System.Web.pdb (to match the lookup path). After that i encountered this:

And it turned out that the mismatching builds are only good for browsing the source, not debugging. (Current machine has VS2012 RC, hence MVC libraries are not RTM). If they match, you'll the the source.
I still don't know why doesn't the lookup path adjust to symbol configuration. Hope this helps.