I'm trying to debug a third-party library. I have it's .pdb and sources. I put .pdb near my dlls. When I step-into third-party code for the first time, VS2012 asks where are the sources. I pick the correct file and everything is fine. Now, I'm rebuilding my code with another version of the same third-party lib. I have another version's .pdb and sources. When I step-into, it doesn't ask where are the sources, instead, it just connects to the SAME SOURCES it connected at the first place. I can close the file and open file from new sources, but each time I press F11 to step-into another file, it continues to open files from the old location.
Visual Studio remembered the selection you made and stored it in the hidden .suo file in the solution directory. You can edit it. First ensure that the Solution Explorer window displays the solution name (similar to "Solution 'name' (x projects)"). If not then use Tools + Options, Projects and Solutions, tick the "Always show solution" checkbox.
Right-click the solution in the Solution Explorer window, Properties, Debug Source Files setting. You should see the directory you added in the original debug sessions. Delete it and add the new directory.