Arg! I have a custom \"harness\" executable running my class library project. Every time I step into the harness\'s code, I get that \"No Source Available\" pane popping up.
Here is a link to an add-in that correct the bug:
http://visualstudiogallery.msdn.microsoft.com/en-us/fdbb2036-471e-40a7-b20e-31f8fd5578fa
This work great for me.